{"id":81399,"date":"2024-11-25T09:17:21","date_gmt":"2024-11-25T02:17:21","guid":{"rendered":"https:\/\/itviec.com\/blog\/?p=81399"},"modified":"2024-11-25T09:17:21","modified_gmt":"2024-11-25T02:17:21","slug":"cau-hoi-phong-van-ios-developer","status":"publish","type":"post","link":"https:\/\/itviec.com\/blog\/cau-hoi-phong-van-ios-developer\/","title":{"rendered":"Top 40+ c\u00e2u h\u1ecfi ph\u1ecfng v\u1ea5n  iOS Developer th\u01b0\u1eddng g\u1eb7p"},"content":{"rendered":"<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_84 counter-hierarchy ez-toc-counter ez-toc-grey ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">N\u1ed9i dung b\u00e0i vi\u1ebft<\/p>\n<span class=\"ez-toc-title-toggle\"><a href=\"#\" class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" aria-label=\"Toggle Table of Content\"><span class=\"ez-toc-js-icon-con\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/span><\/a><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/itviec.com\/blog\/cau-hoi-phong-van-ios-developer\/#iOS_Developer_la_ai_Cong_viec_cua_iOS_Developer_la_gi\" >iOS Developer l\u00e0 ai? C\u00f4ng vi\u1ec7c c\u1ee7a iOS Developer l\u00e0 g\u00ec?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/itviec.com\/blog\/cau-hoi-phong-van-ios-developer\/#Cac_cau_hoi_phong_van_iOS_Developer_lien_quan_den_Swift_va_Objective-C\" >C\u00e1c c\u00e2u h\u1ecfi ph\u1ecfng v\u1ea5n iOS Developer li\u00ean quan \u0111\u1ebfn Swift v\u00e0 Objective-C<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/itviec.com\/blog\/cau-hoi-phong-van-ios-developer\/#Cac_cau_hoi_phong_van_iOS_Developer_lien_quan_den_iOS_SDK\" >C\u00e1c c\u00e2u h\u1ecfi ph\u1ecfng v\u1ea5n iOS Developer li\u00ean quan \u0111\u1ebfn iOS SDK<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/itviec.com\/blog\/cau-hoi-phong-van-ios-developer\/#Cac_cau_hoi_phong_van_iOS_Developer_lien_quan_den_UIUX_Kien_truc\" >C\u00e1c c\u00e2u h\u1ecfi ph\u1ecfng v\u1ea5n iOS Developer li\u00ean quan \u0111\u1ebfn UI\/UX &amp; Ki\u1ebfn tr\u00fac<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/itviec.com\/blog\/cau-hoi-phong-van-ios-developer\/#Cac_cau_hoi_phong_van_lien_quan_den_toi_uu_hoa_hieu_nang\" >C\u00e1c c\u00e2u h\u1ecfi ph\u1ecfng v\u1ea5n li\u00ean quan \u0111\u1ebfn t\u1ed1i \u01b0u ho\u00e1 hi\u1ec7u n\u0103ng\u00a0<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/itviec.com\/blog\/cau-hoi-phong-van-ios-developer\/#Tong_ket_cau_hoi_phong_van_iOS_Developer\" >T\u1ed5ng k\u1ebft c\u00e2u h\u1ecfi ph\u1ecfng v\u1ea5n iOS Developer<\/a><\/li><\/ul><\/nav><\/div>\n<p><em><strong>iOS Developer l\u00e0 chuy\u00ean gia t\u1ea1o \u1ee9ng d\u1ee5ng cho h\u1ec7 \u0111i\u1ec1u h\u00e0nh iOS c\u1ee7a Apple. Nh\u1eefng nh\u00e0 ph\u00e1t tri\u1ec3n n\u00e0y c\u00f3 hi\u1ec3u bi\u1ebft s\u00e2u s\u1eafc v\u1ec1 h\u1ec7 sinh th\u00e1i iOS. B\u00e0i vi\u1ebft sau \u0111\u00e2y s\u1ebd t\u1ed5ng h\u1ee3p c\u00e1c c\u00e2u h\u1ecfi ph\u1ecfng v\u1ea5n iOS Developer ph\u1ed5 bi\u1ebfn, bao g\u1ed3m c\u00e1c ch\u1ee7 \u0111\u1ec1 v\u1ec1 framework, h\u01b0\u1edbng d\u1eabn thi\u1ebft k\u1ebf v\u00e0 ng\u00f4n ng\u1eef l\u1eadp tr\u00ecnh, ch\u1ee7 y\u1ebfu l\u00e0 Swift v\u00e0 Objective-C.<\/strong><\/em><\/p>\n<p><span style=\"font-weight: 400;\">B\u00e0i vi\u1ebft n\u00e0y s\u1ebd t\u1eadp trung t\u1ed5ng h\u1ee3p c\u00e1c c\u00e2u h\u1ecfi ph\u1ecfng v\u1ea5n iOS Developer c\u00f3 li\u00ean quan \u0111\u1ebfn c\u00e1c ch\u1ee7 \u0111\u1ec1:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">C\u00e1c c\u00e2u h\u1ecfi ph\u1ecfng v\u1ea5n iOS Developer li\u00ean quan \u0111\u1ebfn Swift v\u00e0 Objective-C<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">C\u00e1c c\u00e2u h\u1ecfi ph\u1ecfng v\u1ea5n iOS Developer li\u00ean quan \u0111\u1ebfn iOS SDK<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">C\u00e1c c\u00e2u h\u1ecfi ph\u1ecfng v\u1ea5n iOS Developer li\u00ean quan \u0111\u1ebfn UI\/UX v\u00e0 ki\u1ebfn tr\u00fac<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">C\u00e1c c\u00e2u h\u1ecfi ph\u1ecfng v\u1ea5n iOS Developer t\u1ed1i \u01b0u ho\u00e1 hi\u1ec7u n\u0103ng<\/span><\/li>\n<\/ul>\n<h2><span class=\"ez-toc-section\" id=\"iOS_Developer_la_ai_Cong_viec_cua_iOS_Developer_la_gi\"><\/span><strong>iOS Developer l\u00e0 ai? C\u00f4ng vi\u1ec7c c\u1ee7a iOS Developer l\u00e0 g\u00ec?<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>iOS Developer ch\u1ecbu tr\u00e1ch nhi\u1ec7m thi\u1ebft k\u1ebf, x\u00e2y d\u1ef1ng, ki\u1ec3m th\u1eed v\u00e0 duy tr\u00ec c\u00e1c \u1ee9ng d\u1ee5ng di \u0111\u1ed9ng tr\u00ean n\u1ec1n t\u1ea3ng iOS, \u0111\u1ea3m b\u1ea3o ch\u00fang \u0111\u00e1p \u1ee9ng nhu c\u1ea7u ng\u01b0\u1eddi d\u00f9ng v\u00e0 mang l\u1ea1i tr\u1ea3i nghi\u1ec7m m\u01b0\u1ee3t m\u00e0.<\/p>\n<p>H\u1ecd c\u1ea7n th\u00e0nh th\u1ea1o ng\u00f4n ng\u1eef l\u1eadp tr\u00ecnh Swift v\u00e0 Objective-C, hi\u1ec3u bi\u1ebft s\u00e2u v\u1ec1 ki\u1ebfn tr\u00fac iOS, c\u00e1c nguy\u00ean l\u00fd ph\u00e1t tri\u1ec3n \u1ee9ng d\u1ee5ng di \u0111\u1ed9ng, v\u00e0 c\u00f3 kinh nghi\u1ec7m t\u00edch h\u1ee3p API c\u1ee7a b\u00ean th\u1ee9 ba.<\/p>\n<p>B\u00ean c\u1ea1nh k\u1ef9 n\u0103ng chuy\u00ean m\u00f4n, iOS Developer c\u1ea7n kh\u1ea3 n\u0103ng gi\u1ea3i quy\u1ebft v\u1ea5n \u0111\u1ec1, l\u00e0m vi\u1ec7c nh\u00f3m v\u00e0 c\u1eadp nh\u1eadt nhanh c\u00e1c xu h\u01b0\u1edbng c\u00f4ng ngh\u1ec7 m\u1edbi. C\u00e1c c\u00f4ng c\u1ee5 c\u1ea7n thi\u1ebft cho c\u00f4ng vi\u1ec7c n\u00e0y bao g\u1ed3m Xcode, Git, v\u00e0 c\u00e1c th\u01b0 vi\u1ec7n nh\u01b0 Alamofire, CoreData, c\u00f9ng v\u1edbi c\u00e1c c\u00f4ng c\u1ee5 ki\u1ec3m th\u1eed v\u00e0 CI\/CD \u0111\u1ec3 h\u1ed7 tr\u1ee3 ph\u00e1t tri\u1ec3n \u1ee9ng d\u1ee5ng hi\u1ec7u qu\u1ea3.<\/p>\n<p>Tr\u01b0\u1edbc khi \u0111i v\u00e0o danh s\u00e1ch c\u00e1c c\u00e2u h\u1ecfi ph\u1ecfng v\u1ea5n iOS Developer sau, b\u1ea1n n\u00ean &#8220;\u00f4n t\u1eadp&#8221; ki\u1ebfn th\u1ee9c v\u1edbi c\u00e1c b\u00e0i vi\u1ebft sau \u0111\u00e2y:<\/p>\n<ul>\n<li><a href=\"https:\/\/itviec.com\/blog\/lap-trinh-ios\/\" target=\"_blank\" rel=\"noopener\">L\u1eadp tr\u00ecnh iOS l\u00e0 g\u00ec? C\u00e1c b\u01b0\u1edbc b\u1eaft \u0111\u1ea7u v\u1edbi l\u1eadp tr\u00ecnh iOS<\/a><\/li>\n<li><a href=\"https:\/\/itviec.com\/blog\/hoc-lap-trinh-ios\/\" target=\"_blank\" rel=\"noopener\">H\u1ecdc l\u1eadp tr\u00ecnh iOS to\u00e0n di\u1ec7n v\u1edbi 5 b\u01b0\u1edbc chi ti\u1ebft cho ng\u01b0\u1eddi m\u1edbi<\/a><\/li>\n<li><a href=\"https:\/\/itviec.com\/blog\/tai-lieu-lap-trinh-ios\/\" target=\"_blank\" rel=\"noopener\">11 t\u00e0i li\u1ec7u l\u1eadp tr\u00ecnh iOS mi\u1ec5n ph\u00ed hay nh\u1ea5t<\/a><\/li>\n<li><a href=\"https:\/\/itviec.com\/blog\/cau-hoi-phong-van-mobile-developer\/\" target=\"_blank\" rel=\"noopener\">Top 40+ c\u00e2u h\u1ecfi ph\u1ecfng v\u1ea5n Mobile Developer ph\u1ed5 bi\u1ebfn<\/a><\/li>\n<\/ul>\n<p>N\u1ebfu b\u1ea1n l\u00e0 Android Developer, b\u1ea1n n\u00ean tham kh\u1ea3o <a href=\"https:\/\/itviec.com\/blog\/cau-hoi-phong-van-android-developer\/\" target=\"_blank\" rel=\"noopener\"><strong>Top 40+ c\u00e2u h\u1ecfi ph\u1ecfng v\u1ea5n Android Developer<\/strong><\/a>.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Cac_cau_hoi_phong_van_iOS_Developer_lien_quan_den_Swift_va_Objective-C\"><\/span><strong>C\u00e1c c\u00e2u h\u1ecfi ph\u1ecfng v\u1ea5n iOS Developer li\u00ean quan \u0111\u1ebfn Swift v\u00e0 Objective-C<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n<h3><strong>B\u1ea1n \u0111\u00e3 t\u1eebng l\u00e0m vi\u1ec7c v\u1edbi c\u1ea3 Swift v\u00e0 Objective-C ch\u01b0a? N\u1ebfu c\u00f3, b\u1ea1n c\u00f3 th\u1ec3 so s\u00e1nh c\u00e1ch x\u1eed l\u00fd b\u1ed9 nh\u1edb trong hai ng\u00f4n ng\u1eef n\u00e0y kh\u00f4ng?<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">Trong Objective-C, b\u1ed9 nh\u1edb \u0111\u01b0\u1ee3c qu\u1ea3n l\u00fd th\u1ee7 c\u00f4ng b\u1eb1ng c\u00e1ch s\u1eed d\u1ee5ng <\/span><a href=\"https:\/\/fullonrager.github.io\/rys-objective-c-tutorial-archive\/memory-management.html\" target=\"_blank\" rel=\"noopener\"><span style=\"font-weight: 400;\">retain\/release ho\u1eb7c autorelease<\/span><\/a><span style=\"font-weight: 400;\">, \u0111i\u1ec1u n\u00e0y d\u1ec5 d\u1eabn \u0111\u1ebfn r\u00f2 r\u1ec9 b\u1ed9 nh\u1edb n\u1ebfu kh\u00f4ng c\u1ea9n th\u1eadn.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Trong khi \u0111\u00f3, Swift s\u1eed d\u1ee5ng ARC (<\/span><a href=\"https:\/\/docs.swift.org\/swift-book\/documentation\/the-swift-programming-language\/automaticreferencecounting\/\" target=\"_blank\" rel=\"noopener\"><span style=\"font-weight: 400;\">Automatic Reference Counting<\/span><\/a><span style=\"font-weight: 400;\">), gi\u00fap t\u1ef1 \u0111\u1ed9ng qu\u1ea3n l\u00fd b\u1ed9 nh\u1edb b\u1eb1ng c\u00e1ch theo d\u00f5i s\u1ed1 tham chi\u1ebfu \u0111\u1ebfn c\u00e1c \u0111\u1ed1i t\u01b0\u1ee3ng v\u00e0 gi\u1ea3i ph\u00f3ng ch\u00fang khi kh\u00f4ng c\u00f2n \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng. \u0110i\u1ec1u n\u00e0y gi\u00fap \u0111\u01a1n gi\u1ea3n h\u00f3a quy tr\u00ecnh ph\u00e1t tri\u1ec3n v\u00e0 gi\u1ea3m thi\u1ec3u l\u1ed7i li\u00ean quan \u0111\u1ebfn qu\u1ea3n l\u00fd b\u1ed9 nh\u1edb.<\/span><\/p>\n<h3><strong>S\u1ef1 kh\u00e1c bi\u1ec7t gi\u1eefa class v\u00e0 struct trong Swift l\u00e0 g\u00ec?<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">Trong Swift, <\/span><span style=\"font-weight: 400;\">class<\/span><span style=\"font-weight: 400;\"> v\u00e0 <\/span><span style=\"font-weight: 400;\">struct<\/span><span style=\"font-weight: 400;\"> \u0111\u1ec1u \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng \u0111\u1ec3 t\u1ea1o ra c\u00e1c ki\u1ec3u d\u1eef li\u1ec7u t\u00f9y ch\u1ec9nh, nh\u01b0ng c\u00f3 m\u1ed9t s\u1ed1 kh\u00e1c bi\u1ec7t ch\u00ednh:<\/span><\/p>\n<table>\n<tbody>\n<tr>\n<td><span style=\"font-weight: 400;\">\u0110\u1eb7c \u0111i\u1ec3m\u00a0<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Class\u00a0<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Struct\u00a0<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">Ki\u1ec3u<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Tham chi\u1ebfu (Reference type)<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Gi\u00e1 tr\u1ecb (Value type)<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">K\u1ebf th\u1eeba<\/span><\/td>\n<td><span style=\"font-weight: 400;\">H\u1ed7 tr\u1ee3 k\u1ebf th\u1eeba\u00a0<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Kh\u00f4ng h\u1ed7 tr\u1ee3 k\u1ebf th\u1eeba\u00a0<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">Deinitializer<\/span><\/td>\n<td><span style=\"font-weight: 400;\">C\u00f3 th\u1ec3 c\u00f3 deinitializers<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Kh\u00f4ng c\u00f3 deinitializers<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">Mutability<\/span><\/td>\n<td><span style=\"font-weight: 400;\">C\u00f3 th\u1ec3 thay \u0111\u1ed5i thu\u1ed9c t\u00ednh khi bi\u1ebfn \u0111\u01b0\u1ee3c khai b\u00e1o l\u00e0 <\/span><span style=\"font-weight: 400;\">var<\/span><span style=\"font-weight: 400;\"> v\u00e0 c\u00f3 th\u1ec3 thay \u0111\u1ed5i ngay c\u1ea3 khi l\u00e0 <\/span><span style=\"font-weight: 400;\">let<\/span><span style=\"font-weight: 400;\"> trong m\u1ed9t ph\u1ea1m vi kh\u00f4ng thay \u0111\u1ed5i.<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Kh\u00f4ng th\u1ec3 thay \u0111\u1ed5i thu\u1ed9c t\u00ednh khi bi\u1ebfn \u0111\u01b0\u1ee3c khai b\u00e1o l\u00e0 <\/span><span style=\"font-weight: 400;\">let<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">Sao ch\u00e9p<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Sao ch\u00e9p tham chi\u1ebfu \u0111\u1ebfn \u0111\u1ed1i t\u01b0\u1ee3ng (c\u1ea3 hai bi\u1ebfn \u0111\u1ec1u tham chi\u1ebfu c\u00f9ng m\u1ed9t \u0111\u1ed1i t\u01b0\u1ee3ng)<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Sao ch\u00e9p gi\u00e1 tr\u1ecb (t\u1ea1o b\u1ea3n sao \u0111\u1ed9c l\u1eadp)<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">C\u1ea5u tr\u00fac d\u1eef li\u1ec7u<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Th\u00edch h\u1ee3p cho c\u00e1c \u0111\u1ed1i t\u01b0\u1ee3ng ph\u1ee9c t\u1ea1p, c\u1ea7n k\u1ebf th\u1eeba v\u00e0 chia s\u1ebb tr\u1ea1ng th\u00e1i.<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Th\u00edch h\u1ee3p cho c\u00e1c ki\u1ec3u d\u1eef li\u1ec7u \u0111\u01a1n gi\u1ea3n, kh\u00f4ng c\u1ea7n chia s\u1ebb tr\u1ea1ng th\u00e1i.<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h3><strong>Gi\u1ea3i th\u00edch t\u1eeb kh\u00f3a optional trong Swift. T\u1ea1i sao c\u1ea7n s\u1eed d\u1ee5ng n\u00f3?<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">Optional l\u00e0 m\u1ed9t lo\u1ea1i ki\u1ec3u d\u1eef li\u1ec7u \u0111\u1eb7c bi\u1ec7t trong Swift, cho ph\u00e9p m\u1ed9t bi\u1ebfn c\u00f3 th\u1ec3 ch\u1ee9a gi\u00e1 tr\u1ecb ho\u1eb7c kh\u00f4ng c\u00f3 gi\u00e1 tr\u1ecb (nil). \u0110i\u1ec1u n\u00e0y gi\u00fap l\u1eadp tr\u00ecnh vi\u00ean x\u1eed l\u00fd c\u00e1c tr\u01b0\u1eddng h\u1ee3p m\u00e0 m\u1ed9t gi\u00e1 tr\u1ecb c\u00f3 th\u1ec3 kh\u00f4ng t\u1ed3n t\u1ea1i m\u00e0 kh\u00f4ng g\u1eb7p ph\u1ea3i l\u1ed7i trong qu\u00e1 tr\u00ecnh th\u1ef1c thi.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">\u0110\u1ec3 khai b\u00e1o m\u1ed9t bi\u1ebfn l\u00e0 optional, b\u1ea1n s\u1eed d\u1ee5ng d\u1ea5u h\u1ecfi (?) sau ki\u1ec3u d\u1eef li\u1ec7u:<\/span><\/p>\n<pre>var name: String? \/\/ name c\u00f3 th\u1ec3 l\u00e0 String ho\u1eb7c nil<\/pre>\n<p><span style=\"font-weight: 400;\">L\u1ee3i \u00edch c\u1ee7a vi\u1ec7c s\u1eed d\u1ee5ng Optional<\/span><\/p>\n<ol>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">An to\u00e0n v\u1edbi nil: Optional gi\u00fap tr\u00e1nh c\u00e1c l\u1ed7i runtime khi c\u1ed1 g\u1eafng truy c\u1eadp v\u00e0o gi\u00e1 tr\u1ecb nil, m\u1ed9t v\u1ea5n \u0111\u1ec1 ph\u1ed5 bi\u1ebfn trong c\u00e1c ng\u00f4n ng\u1eef l\u1eadp tr\u00ecnh kh\u00e1c. Thay v\u00ec x\u1ea3y ra l\u1ed7i, b\u1ea1n c\u00f3 th\u1ec3 ki\u1ec3m tra s\u1ef1 t\u1ed3n t\u1ea1i c\u1ee7a gi\u00e1 tr\u1ecb tr\u01b0\u1edbc khi s\u1eed d\u1ee5ng n\u00f3.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">R\u00f5 r\u00e0ng trong thi\u1ebft k\u1ebf: Vi\u1ec7c s\u1eed d\u1ee5ng optional l\u00e0m cho m\u00e3 ngu\u1ed3n r\u00f5 r\u00e0ng h\u01a1n v\u1ec1 m\u1eb7t \u00fd ngh\u0129a. Khi m\u1ed9t bi\u1ebfn \u0111\u01b0\u1ee3c khai b\u00e1o l\u00e0 optional, n\u00f3 th\u00f4ng b\u00e1o cho l\u1eadp tr\u00ecnh vi\u00ean r\u1eb1ng gi\u00e1 tr\u1ecb c\u00f3 th\u1ec3 kh\u00f4ng t\u1ed3n t\u1ea1i, t\u1eeb \u0111\u00f3 y\u00eau c\u1ea7u ph\u1ea3i ki\u1ec3m tra tr\u01b0\u1edbc khi s\u1eed d\u1ee5ng.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">H\u1ed7 tr\u1ee3 unwrapping: Swift cung c\u1ea5p c\u00e1c k\u1ef9 thu\u1eadt unwrapping an to\u00e0n \u0111\u1ec3 truy c\u1eadp v\u00e0o gi\u00e1 tr\u1ecb c\u1ee7a optional, nh\u01b0 <\/span><span style=\"font-weight: 400;\">if let<\/span><span style=\"font-weight: 400;\"> ho\u1eb7c <\/span><span style=\"font-weight: 400;\">guard let<\/span><span style=\"font-weight: 400;\">. \u0110i\u1ec1u n\u00e0y gi\u00fap d\u1ec5 d\u00e0ng qu\u1ea3n l\u00fd c\u00e1c t\u00ecnh hu\u1ed1ng c\u00f3 th\u1ec3 x\u1ea3y ra v\u1edbi nil m\u00e0 kh\u00f4ng l\u00e0m t\u0103ng \u0111\u1ed9 ph\u1ee9c t\u1ea1p.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">H\u1ed7 tr\u1ee3 chaining: B\u1ea1n c\u00f3 th\u1ec3 s\u1eed d\u1ee5ng optional chaining \u0111\u1ec3 g\u1ecdi ph\u01b0\u01a1ng th\u1ee9c ho\u1eb7c thu\u1ed9c t\u00ednh c\u1ee7a m\u1ed9t optional m\u00e0 kh\u00f4ng c\u1ea7n ki\u1ec3m tra nil m\u1ed7i l\u1ea7n.<\/span><\/li>\n<\/ol>\n<p><span style=\"font-weight: 400;\">Khi n\u00e0o c\u1ea7n s\u1eed d\u1ee5ng Optional?<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Khi b\u1ea1n c\u1ea7n m\u1ed9t bi\u1ebfn c\u00f3 th\u1ec3 kh\u00f4ng c\u00f3 gi\u00e1 tr\u1ecb h\u1ee3p l\u1ec7.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Khi b\u1ea1n l\u00e0m vi\u1ec7c v\u1edbi d\u1eef li\u1ec7u kh\u00f4ng x\u00e1c \u0111\u1ecbnh, ch\u1eb3ng h\u1ea1n nh\u01b0 d\u1eef li\u1ec7u t\u1eeb API, n\u01a1i m\u1ed9t s\u1ed1 tr\u01b0\u1eddng c\u00f3 th\u1ec3 kh\u00f4ng c\u00f3 gi\u00e1 tr\u1ecb.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Khi b\u1ea1n mu\u1ed1n bi\u1ec3u th\u1ecb r\u00f5 r\u00e0ng r\u1eb1ng m\u1ed9t gi\u00e1 tr\u1ecb c\u00f3 th\u1ec3 t\u1ed3n t\u1ea1i ho\u1eb7c kh\u00f4ng t\u1ed3n t\u1ea1i, nh\u1eb1m n\u00e2ng cao \u0111\u1ed9 an to\u00e0n v\u00e0 r\u00f5 r\u00e0ng c\u1ee7a m\u00e3 ngu\u1ed3n.<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">T\u00ecm hi\u1ec3u th\u00eam t\u1ea1i: <\/span><a href=\"https:\/\/developer.apple.com\/documentation\/swift\/optional\" target=\"_blank\" rel=\"noopener\"><span style=\"font-weight: 400;\">https:\/\/developer.apple.com\/documentation\/swift\/optional<\/span><\/a><\/p>\n<h3><strong>guard v\u00e0 if let trong Swift kh\u00e1c nhau nh\u01b0 th\u1ebf n\u00e0o? Khi n\u00e0o n\u00ean s\u1eed d\u1ee5ng m\u1ed7i lo\u1ea1i?<\/strong><\/h3>\n<table>\n<tbody>\n<tr>\n<td><span style=\"font-weight: 400;\">\u0110\u1eb7c \u0111i\u1ec3m<\/span><\/td>\n<td><span style=\"font-weight: 400;\">if let\u00a0<\/span><\/td>\n<td><span style=\"font-weight: 400;\">guard let<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">C\u00fa ph\u00e1p\u00a0<\/span><\/td>\n<td><span style=\"font-weight: 400;\">\u0110\u01b0\u1ee3c s\u1eed d\u1ee5ng b\u00ean trong m\u1ed9t kh\u1ed1i l\u1ec7nh, v\u00e0 khi \u0111i\u1ec1u ki\u1ec7n th\u1ecfa m\u00e3n, kh\u1ed1i l\u1ec7nh <\/span><span style=\"font-weight: 400;\">if<\/span><span style=\"font-weight: 400;\"> s\u1ebd \u0111\u01b0\u1ee3c th\u1ef1c thi.<\/span><\/td>\n<td><span style=\"font-weight: 400;\">\u0110\u01b0\u1ee3c s\u1eed d\u1ee5ng \u0111\u1ec3 ki\u1ec3m tra \u0111i\u1ec1u ki\u1ec7n, v\u00e0 y\u00eau c\u1ea7u <\/span><span style=\"font-weight: 400;\">else<\/span><span style=\"font-weight: 400;\"> \u0111\u1ec3 tho\u00e1t ra kh\u1ecfi ph\u1ea1m vi hi\u1ec7n t\u1ea1i n\u1ebfu \u0111i\u1ec1u ki\u1ec7n kh\u00f4ng th\u1ecfa m\u00e3n.<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">Ph\u1ea1m vi s\u1eed d\u1ee5ng<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Gi\u00e1 tr\u1ecb \u0111\u01b0\u1ee3c unwrapped ch\u1ec9 t\u1ed3n t\u1ea1i b\u00ean trong kh\u1ed1i l\u1ec7nh <\/span><span style=\"font-weight: 400;\">if<\/span><span style=\"font-weight: 400;\">.<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Gi\u00e1 tr\u1ecb \u0111\u01b0\u1ee3c unwrapped t\u1ed3n t\u1ea1i b\u00ean ngo\u00e0i kh\u1ed1i l\u1ec7nh <\/span><span style=\"font-weight: 400;\">guard<\/span><span style=\"font-weight: 400;\">, trong ph\u1ea1m vi hi\u1ec7n t\u1ea1i.<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">\u00dd ngh\u0129a logic<\/span><\/td>\n<td><span style=\"font-weight: 400;\">D\u00f9ng \u0111\u1ec3 th\u1ef1c hi\u1ec7n c\u00e1c h\u00e0nh \u0111\u1ed9ng kh\u00e1c nhau d\u1ef1a tr\u00ean vi\u1ec7c c\u00f3 gi\u00e1 tr\u1ecb hay kh\u00f4ng.<\/span><\/td>\n<td><span style=\"font-weight: 400;\">D\u00f9ng \u0111\u1ec3 \u0111\u1ea3m b\u1ea3o r\u1eb1ng \u0111i\u1ec1u ki\u1ec7n \u0111\u01b0\u1ee3c th\u1ecfa m\u00e3n tr\u01b0\u1edbc khi ti\u1ebfp t\u1ee5c th\u1ef1c thi logic ph\u00eda sau. N\u1ebfu kh\u00f4ng th\u1ecfa m\u00e3n, th\u01b0\u1eddng k\u1ebft th\u00fac ho\u1eb7c tho\u00e1t kh\u1ecfi h\u00e0m.<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">T\u00ednh t\u01b0\u1eddng minh<\/span><\/td>\n<td><span style=\"font-weight: 400;\">T\u1ed1t h\u01a1n khi x\u1eed l\u00fd c\u00e1c tr\u01b0\u1eddng h\u1ee3p m\u00e0 c\u1ea3 hai nh\u00e1nh \u0111\u1ec1u quan tr\u1ecdng (c\u00f3 ho\u1eb7c kh\u00f4ng c\u00f3 gi\u00e1 tr\u1ecb).<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Th\u01b0\u1eddng \u0111\u01b0\u1ee3c d\u00f9ng \u0111\u1ec3 gi\u1ea3m \u0111\u1ed9 s\u00e2u c\u1ee7a m\u00e3 v\u00e0 l\u00e0m r\u00f5 y\u00eau c\u1ea7u ki\u1ec3m tra ngay t\u1eeb \u0111\u1ea7u.<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">S\u1eed d\u1ee5ng <\/span><span style=\"font-weight: 400;\">if let<\/span><span style=\"font-weight: 400;\"> khi:<\/span>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">B\u1ea1n ch\u1ec9 mu\u1ed1n x\u1eed l\u00fd gi\u00e1 tr\u1ecb \u0111\u00e3 \u0111\u01b0\u1ee3c unwrapped trong m\u1ed9t ph\u1ea1m vi nh\u1ecf.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">C\u1ea3 hai tr\u01b0\u1eddng h\u1ee3p c\u00f3 v\u00e0 kh\u00f4ng c\u00f3 gi\u00e1 tr\u1ecb \u0111\u1ec1u c\u1ea7n x\u1eed l\u00fd logic c\u1ee5 th\u1ec3.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">B\u1ea1n mu\u1ed1n th\u1ef1c hi\u1ec7n c\u00e1c h\u00e0nh \u0111\u1ed9ng kh\u00e1c nhau d\u1ef1a tr\u00ean vi\u1ec7c c\u00f3 gi\u00e1 tr\u1ecb hay kh\u00f4ng.<\/span><\/li>\n<\/ul>\n<\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">S\u1eed d\u1ee5ng <\/span><span style=\"font-weight: 400;\">guard let<\/span><span style=\"font-weight: 400;\"> khi:<\/span>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">B\u1ea1n mu\u1ed1n \u0111\u1ea3m b\u1ea3o r\u1eb1ng gi\u00e1 tr\u1ecb \u0111\u00e3 \u0111\u01b0\u1ee3c unwrapped v\u00e0 ti\u1ebfp t\u1ee5c x\u1eed l\u00fd ph\u1ea7n logic ph\u00eda sau.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">B\u1ea1n mu\u1ed1n gi\u1ea3m \u0111\u1ed9 s\u00e2u c\u1ee7a m\u00e3 ngu\u1ed3n (tr\u00e1nh vi\u1ebft qu\u00e1 nhi\u1ec1u kh\u1ed1i <\/span><span style=\"font-weight: 400;\">if<\/span><span style=\"font-weight: 400;\"> l\u1ed3ng nhau).<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">B\u1ea1n c\u1ea7n d\u1eebng ho\u1eb7c tho\u00e1t kh\u1ecfi m\u1ed9t h\u00e0m s\u1edbm n\u1ebfu m\u1ed9t gi\u00e1 tr\u1ecb kh\u00f4ng t\u1ed3n t\u1ea1i (nil).<\/span><\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p>T\u00f3m l\u1ea1i:<\/p>\n<ul>\n<li><strong>guard let<\/strong><span style=\"font-weight: 400;\"> gi\u00fap m\u00e3 ngu\u1ed3n d\u1ec5 \u0111\u1ecdc h\u01a1n khi b\u1ea1n c\u1ea7n ki\u1ec3m tra nhi\u1ec1u gi\u00e1 tr\u1ecb<\/span><\/li>\n<li><strong>if let<\/strong><span style=\"font-weight: 400;\"> ph\u00f9 h\u1ee3p h\u01a1n cho c\u00e1c t\u00ecnh hu\u1ed1ng ki\u1ec3m tra \u0111\u01a1n gi\u1ea3n, n\u01a1i c\u00f3 nhi\u1ec1u c\u00e1ch x\u1eed l\u00fd kh\u00e1c nhau d\u1ef1a tr\u00ean \u0111i\u1ec1u ki\u1ec7n<\/span><\/li>\n<\/ul>\n<h3><strong>H\u00e0m b\u1eadc cao (higher-order function) trong Swift l\u00e0 g\u00ec? Cho m\u1ed9t v\u00ed d\u1ee5 nh\u01b0 map, filter, ho\u1eb7c reduce<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">H\u00e0m b\u1eadc cao trong Swift l\u00e0 c\u00e1c h\u00e0m c\u00f3 th\u1ec3 nh\u1eadn c\u00e1c h\u00e0m kh\u00e1c l\u00e0m \u0111\u1ed1i s\u1ed1 ho\u1eb7c tr\u1ea3 v\u1ec1 m\u1ed9t h\u00e0m kh\u00e1c. Ch\u00fang gi\u00fap x\u1eed l\u00fd c\u00e1c t\u1eadp h\u1ee3p d\u1eef li\u1ec7u v\u00e0 thao t\u00e1c v\u1edbi c\u00e1c \u0111\u1ed1i t\u01b0\u1ee3ng theo c\u00e1ch ng\u1eafn g\u1ecdn v\u00e0 tr\u1ef1c quan h\u01a1n, b\u1eb1ng c\u00e1ch \u00e1p d\u1ee5ng m\u1ed9t h\u00e0m cho c\u00e1c ph\u1ea7n t\u1eed c\u1ee7a m\u1ed9t m\u1ea3ng ho\u1eb7c m\u1ed9t t\u1eadp h\u1ee3p.<\/span><\/p>\n<blockquote><p><span style=\"font-weight: 400;\">T\u00ecm hi\u1ec3u th\u00eam v\u1ec1 <\/span><a href=\"https:\/\/medium.com\/@nareshkukkala\/higher-order-functions-c141893a7ec1\"><span style=\"font-weight: 400;\">higher-order function<\/span><\/a><\/p><\/blockquote>\n<p><strong>Map<\/strong><\/p>\n<p><span style=\"font-weight: 400;\">map<\/span><span style=\"font-weight: 400;\"> l\u00e0 m\u1ed9t h\u00e0m b\u1eadc cao \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng \u0111\u1ec3 \u00e1p d\u1ee5ng m\u1ed9t h\u00e0m cho m\u1ed7i ph\u1ea7n t\u1eed c\u1ee7a m\u1ed9t m\u1ea3ng, sau \u0111\u00f3 tr\u1ea3 v\u1ec1 m\u1ed9t m\u1ea3ng m\u1edbi ch\u1ee9a k\u1ebft qu\u1ea3 c\u1ee7a c\u00e1c ph\u00e9p bi\u1ebfn \u0111\u1ed5i \u0111\u00f3.<\/span><\/p>\n<pre>let numbers = [1, 2, 3, 4, 5]\r\nlet squaredNumbers = numbers.map { $0 * $0 }\r\nprint(squaredNumbers) \/\/ Output: [1, 4, 9, 16, 25]<\/pre>\n<p><span style=\"font-weight: 400;\">Trong v\u00ed d\u1ee5 tr\u00ean, <\/span><span style=\"font-weight: 400;\">map<\/span><span style=\"font-weight: 400;\"> \u00e1p d\u1ee5ng h\u00e0m <\/span><span style=\"font-weight: 400;\">{ $0 * $0 }<\/span><span style=\"font-weight: 400;\"> l\u00ean m\u1ed7i ph\u1ea7n t\u1eed c\u1ee7a m\u1ea3ng <\/span><span style=\"font-weight: 400;\">numbers<\/span><span style=\"font-weight: 400;\">, t\u1ea1o ra m\u1ed9t m\u1ea3ng m\u1edbi <\/span><span style=\"font-weight: 400;\">squaredNumbers<\/span><span style=\"font-weight: 400;\"> ch\u1ee9a c\u00e1c gi\u00e1 tr\u1ecb b\u00ecnh ph\u01b0\u01a1ng c\u1ee7a t\u1eebng ph\u1ea7n t\u1eed.<\/span><\/p>\n<p><strong>Filer<\/strong><\/p>\n<p><span style=\"font-weight: 400;\">filter<\/span><span style=\"font-weight: 400;\"> l\u00e0 m\u1ed9t h\u00e0m b\u1eadc cao cho ph\u00e9p b\u1ea1n l\u1ecdc c\u00e1c ph\u1ea7n t\u1eed c\u1ee7a m\u1ed9t m\u1ea3ng d\u1ef1a tr\u00ean m\u1ed9t \u0111i\u1ec1u ki\u1ec7n. N\u00f3 tr\u1ea3 v\u1ec1 m\u1ed9t m\u1ea3ng m\u1edbi ch\u1ee9a c\u00e1c ph\u1ea7n t\u1eed \u0111\u00e1p \u1ee9ng \u0111i\u1ec1u ki\u1ec7n \u0111\u00e3 cho.<\/span><\/p>\n<pre>let numbers = [1, 2, 3, 4, 5]\r\nlet evenNumbers = numbers.filter { $0 % 2 == 0 }\r\nprint(evenNumbers) \/\/ Output: [2, 4]<\/pre>\n<p><span style=\"font-weight: 400;\">\u1ede \u0111\u00e2y, <\/span><span style=\"font-weight: 400;\">filter<\/span><span style=\"font-weight: 400;\"> \u00e1p d\u1ee5ng \u0111i\u1ec1u ki\u1ec7n <\/span><span style=\"font-weight: 400;\">{ $0 % 2 == 0 }<\/span><span style=\"font-weight: 400;\"> \u0111\u1ec3 ch\u1ec9 gi\u1eef l\u1ea1i c\u00e1c s\u1ed1 ch\u1eb5n trong m\u1ea3ng <\/span><span style=\"font-weight: 400;\">numbers<\/span><span style=\"font-weight: 400;\">, t\u1ea1o ra m\u1ea3ng m\u1edbi <\/span><span style=\"font-weight: 400;\">evenNumbers<\/span><span style=\"font-weight: 400;\">.<\/span><\/p>\n<p><span style=\"font-weight: 400;\"><strong>Reduce<\/strong>\u00a0<\/span><\/p>\n<p><span style=\"font-weight: 400;\">reduce<\/span><span style=\"font-weight: 400;\"> l\u00e0 m\u1ed9t h\u00e0m b\u1eadc cao \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng \u0111\u1ec3 t\u1ed5ng h\u1ee3p c\u00e1c gi\u00e1 tr\u1ecb c\u1ee7a m\u1ed9t m\u1ea3ng th\u00e0nh m\u1ed9t gi\u00e1 tr\u1ecb duy nh\u1ea5t, b\u1eb1ng c\u00e1ch \u00e1p d\u1ee5ng m\u1ed9t ph\u00e9p to\u00e1n cho t\u1eebng ph\u1ea7n t\u1eed.<\/span><\/p>\n<pre>let numbers = [1, 2, 3, 4, 5]\r\nlet sum = numbers.reduce(\u00ae) { $0 + $1 }\r\nprint(sum) \/\/ Output: 15<\/pre>\n<p><span style=\"font-weight: 400;\">reduce<\/span><span style=\"font-weight: 400;\"> b\u1eaft \u0111\u1ea7u v\u1edbi gi\u00e1 tr\u1ecb ban \u0111\u1ea7u l\u00e0 <\/span><span style=\"font-weight: 400;\">0<\/span><span style=\"font-weight: 400;\">, sau \u0111\u00f3 c\u1ed9ng d\u1ed3n t\u1eebng ph\u1ea7n t\u1eed c\u1ee7a m\u1ea3ng <\/span><span style=\"font-weight: 400;\">numbers<\/span><span style=\"font-weight: 400;\"> \u0111\u1ec3 t\u00ednh t\u1ed5ng. Bi\u1ebfn <\/span><span style=\"font-weight: 400;\">$0<\/span><span style=\"font-weight: 400;\"> \u0111\u1ea1i di\u1ec7n cho t\u1ed5ng t\u1ea1m th\u1eddi, c\u00f2n <\/span><span style=\"font-weight: 400;\">$1<\/span><span style=\"font-weight: 400;\"> l\u00e0 t\u1eebng ph\u1ea7n t\u1eed trong qu\u00e1 tr\u00ecnh l\u1eb7p.<\/span><\/p>\n<h3><strong>lazy trong Swift l\u00e0 g\u00ec v\u00e0 khi n\u00e0o n\u00ean s\u1eed d\u1ee5ng?<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">lazy<\/span><span style=\"font-weight: 400;\"> l\u00e0 m\u1ed9t t\u1eeb kh\u00f3a trong Swift d\u00f9ng \u0111\u1ec3 khai b\u00e1o m\u1ed9t thu\u1ed9c t\u00ednh ch\u1ec9 \u0111\u01b0\u1ee3c kh\u1edfi t\u1ea1o khi n\u00f3 \u0111\u01b0\u1ee3c truy c\u1eadp l\u1ea7n \u0111\u1ea7u ti\u00ean. N\u00f3 tr\u00ec ho\u00e3n vi\u1ec7c kh\u1edfi t\u1ea1o cho \u0111\u1ebfn khi c\u1ea7n thi\u1ebft, gi\u00fap t\u1ed1i \u01b0u h\u00f3a hi\u1ec7u su\u1ea5t v\u00e0 tr\u00e1nh vi\u1ec7c s\u1eed d\u1ee5ng t\u00e0i nguy\u00ean kh\u00f4ng c\u1ea7n thi\u1ebft ngay t\u1eeb \u0111\u1ea7u.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">S\u1eed d\u1ee5ng Lazy cho c\u00e1c tr\u01b0\u1eddng h\u1ee3p sau:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Khi vi\u1ec7c kh\u1edfi t\u1ea1o bi\u1ebfn t\u1ed1n nhi\u1ec1u t\u00e0i nguy\u00ean:<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">N\u1ebfu m\u1ed9t thu\u1ed9c t\u00ednh y\u00eau c\u1ea7u nhi\u1ec1u th\u1eddi gian ho\u1eb7c b\u1ed9 nh\u1edb \u0111\u1ec3 kh\u1edfi t\u1ea1o, v\u00e0 kh\u00f4ng ph\u1ea3i l\u00fac n\u00e0o c\u0169ng c\u1ea7n thi\u1ebft, b\u1ea1n n\u00ean s\u1eed d\u1ee5ng <\/span><span style=\"font-weight: 400;\">lazy<\/span><span style=\"font-weight: 400;\">. Vi\u1ec7c n\u00e0y gi\u00fap tr\u00ec ho\u00e3n vi\u1ec7c kh\u1edfi t\u1ea1o cho \u0111\u1ebfn khi thu\u1ed9c t\u00ednh \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng th\u1ef1c s\u1ef1, t\u1eeb \u0111\u00f3 c\u1ea3i thi\u1ec7n hi\u1ec7u su\u1ea5t.<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Khi thu\u1ed9c t\u00ednh ph\u1ee5 thu\u1ed9c v\u00e0o gi\u00e1 tr\u1ecb c\u1ee7a c\u00e1c thu\u1ed9c t\u00ednh kh\u00e1c:<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">lazy<\/span><span style=\"font-weight: 400;\"> c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng khi thu\u1ed9c t\u00ednh c\u1ea7n truy c\u1eadp c\u00e1c gi\u00e1 tr\u1ecb kh\u00e1c m\u00e0 ch\u01b0a \u0111\u01b0\u1ee3c kh\u1edfi t\u1ea1o t\u1ea1i th\u1eddi \u0111i\u1ec3m \u0111\u1ed1i t\u01b0\u1ee3ng \u0111\u01b0\u1ee3c t\u1ea1o ra. Nh\u1edd <\/span><span style=\"font-weight: 400;\">lazy<\/span><span style=\"font-weight: 400;\">, thu\u1ed9c t\u00ednh n\u00e0y s\u1ebd ch\u1ec9 \u0111\u01b0\u1ee3c kh\u1edfi t\u1ea1o sau khi c\u00e1c thu\u1ed9c t\u00ednh kh\u00e1c \u0111\u00e3 c\u00f3 gi\u00e1 tr\u1ecb.<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Khi b\u1ea1n mu\u1ed1n tr\u00ec ho\u00e3n vi\u1ec7c kh\u1edfi t\u1ea1o \u0111\u1ebfn th\u1eddi \u0111i\u1ec3m c\u1ea7n thi\u1ebft:<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">N\u1ebfu thu\u1ed9c t\u00ednh kh\u00f4ng \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng trong m\u1ecdi tr\u01b0\u1eddng h\u1ee3p, vi\u1ec7c s\u1eed d\u1ee5ng <\/span><span style=\"font-weight: 400;\">lazy<\/span><span style=\"font-weight: 400;\"> gi\u00fap tr\u00e1nh vi\u1ec7c t\u1ea1o ra c\u00e1c \u0111\u1ed1i t\u01b0\u1ee3ng kh\u00f4ng c\u1ea7n thi\u1ebft.<\/span><\/p>\n<h3><strong>Gi\u1ea3i th\u00edch s\u1ef1 kh\u00e1c nhau gi\u1eefa weak v\u00e0 unowned<\/strong><span style=\"font-weight: 400;\"><strong> trong Swift<\/strong><\/span><\/h3>\n<table>\n<tbody>\n<tr>\n<td><span style=\"font-weight: 400;\">\u0110\u1eb7c \u0111i\u1ec3m\u00a0<\/span><\/td>\n<td><span style=\"font-weight: 400;\">weak\u00a0<\/span><\/td>\n<td><span style=\"font-weight: 400;\">unowned<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">B\u1ea3n ch\u1ea5t\u00a0<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Tham chi\u1ebfu y\u1ebfu, kh\u00f4ng gi\u1eef m\u1ea1nh \u0111\u1ed1i t\u01b0\u1ee3ng m\u00e0 n\u00f3 tham chi\u1ebfu.<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Tham chi\u1ebfu kh\u00f4ng s\u1edf h\u1eefu, kh\u00f4ng gi\u1eef m\u1ea1nh \u0111\u1ed1i t\u01b0\u1ee3ng m\u00e0 n\u00f3 tham chi\u1ebfu.<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">Optional<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Ph\u1ea3i khai b\u00e1o l\u00e0 optional (<\/span><span style=\"font-weight: 400;\">SomeClass?<\/span><span style=\"font-weight: 400;\">).<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Kh\u00f4ng ph\u1ea3i l\u00e0 optional (khai b\u00e1o tr\u1ef1c ti\u1ebfp ki\u1ec3u <\/span><span style=\"font-weight: 400;\">SomeClass<\/span><span style=\"font-weight: 400;\">).<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">Khi \u0111\u1ed1i t\u01b0\u1ee3ng b\u1ecb h\u1ee7y<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Tham chi\u1ebfu t\u1ef1 \u0111\u1ed9ng tr\u1edf th\u00e0nh <\/span><span style=\"font-weight: 400;\">nil<\/span><span style=\"font-weight: 400;\">.<\/span><\/td>\n<td><span style=\"font-weight: 400;\">G\u00e2y ra l\u1ed7i runtime n\u1ebfu c\u1ed1 truy c\u1eadp v\u00e0o \u0111\u1ed1i t\u01b0\u1ee3ng \u0111\u00e3 b\u1ecb h\u1ee7y.<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">C\u00fa ph\u00e1p<\/span><\/td>\n<td><span style=\"font-weight: 400;\">weak var someObject: SomeClass?<\/span><\/td>\n<td><span style=\"font-weight: 400;\">unowned var someObject: SomeClass<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">Khi n\u00e0o n\u00ean s\u1eed d\u1ee5ng<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Khi \u0111\u1ed1i t\u01b0\u1ee3ng c\u00f3 th\u1ec3 tr\u1edf th\u00e0nh <\/span><span style=\"font-weight: 400;\">nil<\/span><span style=\"font-weight: 400;\"> sau m\u1ed9t th\u1eddi \u0111i\u1ec3m n\u00e0o \u0111\u00f3.<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Khi ch\u1eafc ch\u1eafn r\u1eb1ng \u0111\u1ed1i t\u01b0\u1ee3ng s\u1ebd kh\u00f4ng b\u1ecb h\u1ee7y tr\u01b0\u1edbc tham chi\u1ebfu <\/span><span style=\"font-weight: 400;\">unowned<\/span><span style=\"font-weight: 400;\">.<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">Tr\u00e1nh retain cycle<\/span><\/td>\n<td><span style=\"font-weight: 400;\">\u0110\u00fang, th\u01b0\u1eddng d\u00f9ng trong c\u00e1c tr\u01b0\u1eddng h\u1ee3p delegate ho\u1eb7c closure.<\/span><\/td>\n<td><span style=\"font-weight: 400;\">\u0110\u00fang, th\u01b0\u1eddng d\u00f9ng khi quan h\u1ec7 cha-con m\u00e0 con ph\u1ee5 thu\u1ed9c v\u00e0o cha.<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p><span style=\"font-weight: 400;\">Vi\u1ec7c ch\u1ecdn gi\u1eefa <\/span><span style=\"font-weight: 400;\">weak<\/span><span style=\"font-weight: 400;\"> v\u00e0 <\/span><span style=\"font-weight: 400;\">unowned<\/span><span style=\"font-weight: 400;\"> ph\u1ee5 thu\u1ed9c v\u00e0o vi\u1ec7c li\u1ec7u \u0111\u1ed1i t\u01b0\u1ee3ng c\u00f3 th\u1ec3 tr\u1edf th\u00e0nh <\/span><span style=\"font-weight: 400;\">nil<\/span><span style=\"font-weight: 400;\"> hay kh\u00f4ng v\u00e0 v\u00f2ng \u0111\u1eddi c\u1ee7a c\u00e1c \u0111\u1ed1i t\u01b0\u1ee3ng li\u00ean quan trong \u1ee9ng d\u1ee5ng c\u1ee7a b\u1ea1n.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">V\u00ed d\u1ee5<\/span><\/p>\n<p><strong>Weak<\/strong><\/p>\n<pre>class Person {\r\n  var name: String\r\n  init(name: String) {\r\n    self.name = name\r\n  }\r\n}\r\n\r\nclass Apartment {\r\n  weak var tenant: Person? \/\/ Tham chi\u1ebfu y\u1ebfu \u0111\u1ebfn m\u1ed9t \u0111\u1ed1i t\u01b0\u1ee3ng `Person`\r\n}\r\n\r\nvar john: Person? = Person (name: \"John\")\r\nvar apartment: Apartment? = Apartment()\r\n\r\napartment?.tenant = john\r\njohn = nil\r\n\/\/ Khi 'john` b\u1ecb g\u00e1n nil, `apartment?.tenant` c\u0169ng tr\u1edf th\u00e0nh nil<\/pre>\n<p><span style=\"font-weight: 400;\">Trong v\u00ed d\u1ee5 tr\u00ean, <\/span><span style=\"font-weight: 400;\">tenant<\/span><span style=\"font-weight: 400;\"> l\u00e0 m\u1ed9t tham chi\u1ebfu y\u1ebfu \u0111\u1ebfn <\/span><span style=\"font-weight: 400;\">Person<\/span><span style=\"font-weight: 400;\">. Khi <\/span><span style=\"font-weight: 400;\">john<\/span><span style=\"font-weight: 400;\"> b\u1ecb g\u00e1n <\/span><span style=\"font-weight: 400;\">nil<\/span><span style=\"font-weight: 400;\">, <\/span><span style=\"font-weight: 400;\">tenant<\/span><span style=\"font-weight: 400;\"> trong <\/span><span style=\"font-weight: 400;\">Apartment<\/span><span style=\"font-weight: 400;\"> c\u0169ng t\u1ef1 \u0111\u1ed9ng tr\u1edf th\u00e0nh <\/span><span style=\"font-weight: 400;\">nil<\/span><span style=\"font-weight: 400;\">.<\/span><\/p>\n<p><strong>Unowned<\/strong><\/p>\n<pre>class Customer {\r\n  var name: String\r\n  var card: CreditCard?\r\n  init(name: String) {\r\n    self.name = name\r\n  }\r\n}\r\n\r\nclass CreditCard {\r\n  unowned var owner: Customer \/\/ Tham chi\u1ebfu kh\u00f4ng s\u1edf h\u1eefu \u0111\u1ebfn 'Customer\r\n  init(owner: Customer) {\r\n    self.owner = owner\r\n  }\r\n}\r\n\r\nvar john: Customer? = Customer (name: \"John\")\r\njohn?.card = CreditCard (owner: john!)\r\n\r\njohn = nil<\/pre>\n<p><span style=\"font-weight: 400;\">Trong v\u00ed d\u1ee5 tr\u00ean, <\/span><span style=\"font-weight: 400;\">CreditCard<\/span><span style=\"font-weight: 400;\"> c\u00f3 m\u1ed9t tham chi\u1ebfu <\/span><span style=\"font-weight: 400;\">unowned<\/span><span style=\"font-weight: 400;\"> \u0111\u1ebfn <\/span><span style=\"font-weight: 400;\">Customer<\/span><span style=\"font-weight: 400;\">, gi\u1ea3 \u0111\u1ecbnh r\u1eb1ng <\/span><span style=\"font-weight: 400;\">Customer<\/span><span style=\"font-weight: 400;\"> s\u1ebd lu\u00f4n t\u1ed3n t\u1ea1i cho \u0111\u1ebfn khi <\/span><span style=\"font-weight: 400;\">CreditCard<\/span><span style=\"font-weight: 400;\"> b\u1ecb h\u1ee7y. Khi <\/span><span style=\"font-weight: 400;\">john<\/span><span style=\"font-weight: 400;\"> b\u1ecb g\u00e1n <\/span><span style=\"font-weight: 400;\">nil<\/span><span style=\"font-weight: 400;\">, \u0111\u1ed1i t\u01b0\u1ee3ng <\/span><span style=\"font-weight: 400;\">CreditCard<\/span><span style=\"font-weight: 400;\"> c\u0169ng s\u1ebd b\u1ecb h\u1ee7y.<\/span><\/p>\n<h3><strong>Enum v\u1edbi associated values<\/strong><span style=\"font-weight: 400;\"><strong> trong Swift l\u00e0 g\u00ec? Cho m\u1ed9t v\u00ed d\u1ee5<\/strong><\/span><\/h3>\n<p><span style=\"font-weight: 400;\">Trong Swift, <\/span><i><span style=\"font-weight: 400;\">enum v\u1edbi associated values<\/span><\/i><span style=\"font-weight: 400;\"> cho ph\u00e9p b\u1ea1n \u0111\u1ecbnh ngh\u0129a c\u00e1c tr\u01b0\u1eddng h\u1ee3p (cases) c\u1ee7a m\u1ed9t <\/span><span style=\"font-weight: 400;\">enum<\/span><span style=\"font-weight: 400;\"> k\u00e8m theo c\u00e1c gi\u00e1 tr\u1ecb b\u1ed5 sung. \u0110i\u1ec1u n\u00e0y gi\u00fap m\u1edf r\u1ed9ng kh\u1ea3 n\u0103ng c\u1ee7a <\/span><span style=\"font-weight: 400;\">enum<\/span><span style=\"font-weight: 400;\">, cho ph\u00e9p m\u1ed7i tr\u01b0\u1eddng h\u1ee3p l\u01b0u tr\u1eef c\u00e1c gi\u00e1 tr\u1ecb c\u1ee5 th\u1ec3 li\u00ean quan \u0111\u1ebfn n\u00f3.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Thay v\u00ec ch\u1ec9 \u0111\u01a1n thu\u1ea7n \u0111\u1ecbnh ngh\u0129a c\u00e1c tr\u01b0\u1eddng h\u1ee3p c\u1ed1 \u0111\u1ecbnh, b\u1ea1n c\u00f3 th\u1ec3 g\u00e1n c\u00e1c gi\u00e1 tr\u1ecb \u0111i k\u00e8m m\u1ed7i l\u1ea7n s\u1eed d\u1ee5ng tr\u01b0\u1eddng h\u1ee3p \u0111\u00f3. M\u1ed7i tr\u01b0\u1eddng h\u1ee3p c\u1ee7a <\/span><span style=\"font-weight: 400;\">enum<\/span><span style=\"font-weight: 400;\"> c\u00f3 th\u1ec3 c\u00f3 m\u1ed9t ho\u1eb7c nhi\u1ec1u gi\u00e1 tr\u1ecb v\u1edbi c\u00e1c ki\u1ec3u d\u1eef li\u1ec7u kh\u00e1c nhau.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">D\u01b0\u1edbi \u0111\u00e2y l\u00e0 v\u00ed d\u1ee5 v\u1ec1 m\u1ed9t <\/span><span style=\"font-weight: 400;\">enum<\/span><span style=\"font-weight: 400;\"> m\u00f4 t\u1ea3 tr\u1ea1ng th\u00e1i c\u1ee7a m\u1ed9t y\u00eau c\u1ea7u m\u1ea1ng (network request) v\u1edbi c\u00e1c gi\u00e1 tr\u1ecb li\u00ean quan:<\/span><\/p>\n<pre><span style=\"font-weight: 400;\">enum NetworkResult {<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0case success(data: Data)<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0case failure(error: String)<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0case loading(progress: Double)<\/span>\r\n<span style=\"font-weight: 400;\">}<\/span><\/pre>\n<p>C\u00e1c tr\u01b0\u1eddng h\u1ee3p:<\/p>\n<ul>\n<li><span style=\"font-weight: 400;\">success<\/span><span style=\"font-weight: 400;\">: Tr\u01b0\u1eddng h\u1ee3p n\u00e0y c\u00f3 m\u1ed9t gi\u00e1 tr\u1ecb \u0111i k\u00e8m l\u00e0 <\/span><span style=\"font-weight: 400;\">data<\/span><span style=\"font-weight: 400;\"> c\u00f3 ki\u1ec3u <\/span><span style=\"font-weight: 400;\">Data<\/span><span style=\"font-weight: 400;\"> (d\u1eef li\u1ec7u t\u1ea3i v\u1ec1 th\u00e0nh c\u00f4ng).<\/span><\/li>\n<li><span style=\"font-weight: 400;\">failure<\/span><span style=\"font-weight: 400;\">: Tr\u01b0\u1eddng h\u1ee3p n\u00e0y c\u00f3 m\u1ed9t gi\u00e1 tr\u1ecb \u0111i k\u00e8m l\u00e0 <\/span><span style=\"font-weight: 400;\">error<\/span><span style=\"font-weight: 400;\"> ki\u1ec3u <\/span><span style=\"font-weight: 400;\">String<\/span><span style=\"font-weight: 400;\"> (th\u00f4ng b\u00e1o l\u1ed7i khi y\u00eau c\u1ea7u th\u1ea5t b\u1ea1i).<\/span><\/li>\n<li><span style=\"font-weight: 400;\">loading<\/span><span style=\"font-weight: 400;\">: Tr\u01b0\u1eddng h\u1ee3p n\u00e0y c\u00f3 m\u1ed9t gi\u00e1 tr\u1ecb \u0111i k\u00e8m l\u00e0 <\/span><span style=\"font-weight: 400;\">progress<\/span><span style=\"font-weight: 400;\"> ki\u1ec3u <\/span><span style=\"font-weight: 400;\">Double<\/span><span style=\"font-weight: 400;\"> (t\u1ef7 l\u1ec7 ho\u00e0n th\u00e0nh c\u1ee7a y\u00eau c\u1ea7u).<\/span><\/li>\n<\/ul>\n<p><strong>C\u00e1ch s\u1eed d\u1ee5ng Enum v\u1edbi Associated Values<\/strong><\/p>\n<p><span style=\"font-weight: 400;\">D\u01b0\u1edbi \u0111\u00e2y l\u00e0 c\u00e1ch s\u1eed d\u1ee5ng enum v\u1edbi c\u00e1c gi\u00e1 tr\u1ecb \u0111i k\u00e8m:<\/span><\/p>\n<pre><span style=\"font-weight: 400;\">let result1 = NetworkResult.success(data: Data())<\/span>\r\n<span style=\"font-weight: 400;\">let result2 = NetworkResult.failure(error: \"Network error\")<\/span>\r\n<span style=\"font-weight: 400;\">let result3 = NetworkResult.loading(progress: 0.5)<\/span>\r\n\r\n<span style=\"font-weight: 400;\">switch result2 {<\/span>\r\n<span style=\"font-weight: 400;\">case .success(let data):<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0print(\"Download succeeded with data: \\(data)\")<\/span>\r\n<span style=\"font-weight: 400;\">case .failure(let error):<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0print(\"Download failed with error: \\(error)\")<\/span>\r\n<span style=\"font-weight: 400;\">case .loading(let progress):<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0print(\"Download in progress: \\(progress * 100)%\")<\/span>\r\n<span style=\"font-weight: 400;\">}<\/span><\/pre>\n<p>Gi\u1ea3i th\u00edch:<\/p>\n<ul>\n<li><span style=\"font-weight: 400;\">Kh\u1edfi t\u1ea1o gi\u00e1 tr\u1ecb: Khi t\u1ea1o c\u00e1c gi\u00e1 tr\u1ecb <\/span><span style=\"font-weight: 400;\">result1<\/span><span style=\"font-weight: 400;\">, <\/span><span style=\"font-weight: 400;\">result2<\/span><span style=\"font-weight: 400;\">, <\/span><span style=\"font-weight: 400;\">result3<\/span><span style=\"font-weight: 400;\">, m\u1ed7i tr\u01b0\u1eddng h\u1ee3p c\u00f3 th\u1ec3 \u0111i k\u00e8m c\u00e1c gi\u00e1 tr\u1ecb t\u01b0\u01a1ng \u1ee9ng.<\/span><\/li>\n<li><span style=\"font-weight: 400;\">S\u1eed d\u1ee5ng <\/span><span style=\"font-weight: 400;\">switch<\/span><span style=\"font-weight: 400;\">: Khi s\u1eed d\u1ee5ng <\/span><span style=\"font-weight: 400;\">switch<\/span><span style=\"font-weight: 400;\">, b\u1ea1n c\u00f3 th\u1ec3 truy xu\u1ea5t c\u00e1c gi\u00e1 tr\u1ecb \u0111i k\u00e8m b\u1eb1ng c\u00e1ch s\u1eed d\u1ee5ng t\u1eeb kh\u00f3a <\/span><span style=\"font-weight: 400;\">let<\/span><span style=\"font-weight: 400;\"> \u0111\u1ec3 nh\u1eadn gi\u00e1 tr\u1ecb t\u1eeb t\u1eebng tr\u01b0\u1eddng h\u1ee3p.<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">T\u00ecm hi\u1ec3u th\u00eam t\u1ea1i: <\/span><a href=\"https:\/\/docs.swift.org\/swift-book\/documentation\/the-swift-programming-language\/enumerations\/\"><span style=\"font-weight: 400;\">https:\/\/docs.swift.org\/swift-book\/documentation\/the-swift-programming-language\/enumerations\/<\/span><\/a><\/p>\n<h3><strong>Codable trong Swift l\u00e0 g\u00ec? L\u00e0m th\u1ebf n\u00e0o \u0111\u1ec3 s\u1eed d\u1ee5ng n\u00f3 \u0111\u1ec3 m\u00e3 h\u00f3a v\u00e0 gi\u1ea3i m\u00e3 JSON?<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">Codable<\/span><span style=\"font-weight: 400;\"> l\u00e0 m\u1ed9t protocol trong Swift gi\u00fap m\u00e3 h\u00f3a (encoding) v\u00e0 gi\u1ea3i m\u00e3 (decoding) d\u1eef li\u1ec7u gi\u1eefa c\u00e1c \u0111\u1ed1i t\u01b0\u1ee3ng Swift v\u00e0 c\u00e1c \u0111\u1ecbnh d\u1ea1ng d\u1eef li\u1ec7u nh\u01b0 JSON. <\/span><span style=\"font-weight: 400;\">Codable<\/span><span style=\"font-weight: 400;\"> k\u1ebft h\u1ee3p hai protocol <\/span><span style=\"font-weight: 400;\">Encodable<\/span><span style=\"font-weight: 400;\"> v\u00e0 <\/span><span style=\"font-weight: 400;\">Decodable<\/span><span style=\"font-weight: 400;\">, gi\u00fap d\u1ec5 d\u00e0ng chuy\u1ec3n \u0111\u1ed5i qua l\u1ea1i gi\u1eefa c\u00e1c ki\u1ec3u d\u1eef li\u1ec7u v\u00e0 JSON, r\u1ea5t h\u1eefu \u00edch khi l\u00e0m vi\u1ec7c v\u1edbi API.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">\u0110\u1ec3 s\u1eed d\u1ee5ng <\/span><span style=\"font-weight: 400;\">Codable<\/span><span style=\"font-weight: 400;\">, c\u1ea7n t\u1ea1o m\u1ed9t struct ho\u1eb7c class tu\u00e2n th\u1ee7 <\/span><span style=\"font-weight: 400;\">Codable<\/span><span style=\"font-weight: 400;\">. V\u00ed d\u1ee5, v\u1edbi m\u1ed9t struct <\/span><span style=\"font-weight: 400;\">User<\/span><span style=\"font-weight: 400;\">:<\/span><\/p>\n<pre>struct User: Codable {\r\n  var id: Int\r\n  var name: String\r\n  var email: String\r\n}<\/pre>\n<p><span style=\"font-weight: 400;\">Gi\u1ea3i m\u00e3 JSON th\u00e0nh \u0111\u1ed1i t\u01b0\u1ee3ng:<\/span><\/p>\n<pre>let jsonString = \"\"\"\r\n{\r\n  \"id\": 1,\r\n  \"name\": \"John Doe\",\r\n  \"email\": \"john@example.com\"\r\n}\r\n\"\"\"\r\n\r\nif let jsonData = jsonString.data(using: .utf8) {\r\n  let user = try? JSONDecoder().decode(User.self, from: jsonData)\r\n}<\/pre>\n<p><span style=\"font-weight: 400;\">M\u00e3 h\u00f3a \u0111\u1ed1i t\u01b0\u1ee3ng th\u00e0nh JSON:<\/span><\/p>\n<pre><span style=\"font-weight: 400;\">let user = User(id: 1, name: \"John Doe\", email: \"john@example.com\")<\/span>\r\n<span style=\"font-weight: 400;\">let jsonData = try? JSONEncoder().encode(user)<\/span>\r\n<span style=\"font-weight: 400;\">let jsonString = String(data: jsonData!, encoding: .utf8)<\/span><\/pre>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Gi\u1ea3i m\u00e3 (<\/span><span style=\"font-weight: 400;\">decode<\/span><span style=\"font-weight: 400;\">): S\u1eed d\u1ee5ng <\/span><span style=\"font-weight: 400;\">JSONDecoder<\/span><span style=\"font-weight: 400;\"> \u0111\u1ec3 chuy\u1ec3n d\u1eef li\u1ec7u JSON th\u00e0nh \u0111\u1ed1i t\u01b0\u1ee3ng Swift.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">M\u00e3 h\u00f3a (<\/span><span style=\"font-weight: 400;\">encode<\/span><span style=\"font-weight: 400;\">): S\u1eed d\u1ee5ng <\/span><span style=\"font-weight: 400;\">JSONEncoder<\/span><span style=\"font-weight: 400;\"> \u0111\u1ec3 chuy\u1ec3n \u0111\u1ed1i t\u01b0\u1ee3ng Swift th\u00e0nh JSON.<\/span><\/li>\n<\/ul>\n<h3><strong>Generics trong Swift l\u00e0 g\u00ec? L\u1ee3i \u00edch c\u1ee7a vi\u1ec7c s\u1eed d\u1ee5ng Generics?<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">Generics<\/span><span style=\"font-weight: 400;\"> trong Swift cho ph\u00e9p b\u1ea1n vi\u1ebft c\u00e1c h\u00e0m, l\u1edbp, struct, ho\u1eb7c enum c\u00f3 th\u1ec3 l\u00e0m vi\u1ec7c v\u1edbi b\u1ea5t k\u1ef3 ki\u1ec3u d\u1eef li\u1ec7u n\u00e0o, thay v\u00ec ch\u1ec9 gi\u1edbi h\u1ea1n \u1edf m\u1ed9t ki\u1ec3u c\u1ee5 th\u1ec3. \u0110i\u1ec1u n\u00e0y gi\u00fap b\u1ea1n vi\u1ebft code t\u1ed5ng qu\u00e1t h\u01a1n, t\u00e1i s\u1eed d\u1ee5ng \u0111\u01b0\u1ee3c v\u1edbi nhi\u1ec1u lo\u1ea1i d\u1eef li\u1ec7u kh\u00e1c nhau.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">V\u00ed d\u1ee5, m\u1ed9t h\u00e0m th\u00f4ng th\u01b0\u1eddng \u0111\u1ec3 ho\u00e1n \u0111\u1ed5i hai s\u1ed1 nguy\u00ean c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c vi\u1ebft nh\u01b0 sau:<\/span><\/p>\n<pre>func swapTwoValues&lt;T&gt;(__ a: inout T, b: inout T) {\r\n  let temp = a\r\n  a = b\r\n  b = temp\r\n}<\/pre>\n<p><span style=\"font-weight: 400;\">H\u00e0m n\u00e0y ch\u1ec9 c\u00f3 th\u1ec3 ho\u00e1n \u0111\u1ed5i <\/span><span style=\"font-weight: 400;\">Int<\/span><span style=\"font-weight: 400;\">. V\u1edbi <\/span><i><span style=\"font-weight: 400;\">Generics<\/span><\/i><span style=\"font-weight: 400;\">, c\u00f3 th\u1ec3 vi\u1ebft m\u1ed9t h\u00e0m ho\u00e1n \u0111\u1ed5i c\u00f3 th\u1ec3 l\u00e0m vi\u1ec7c v\u1edbi b\u1ea5t k\u1ef3 ki\u1ec3u d\u1eef li\u1ec7u n\u00e0o<\/span><\/p>\n<p><span style=\"font-weight: 400;\">\u1ede \u0111\u00e2y, <\/span><span style=\"font-weight: 400;\">T<\/span><span style=\"font-weight: 400;\"> l\u00e0 m\u1ed9t <\/span><i><span style=\"font-weight: 400;\">placeholder<\/span><\/i><span style=\"font-weight: 400;\"> cho ki\u1ec3u d\u1eef li\u1ec7u, v\u00e0 Swift s\u1ebd t\u1ef1 \u0111\u1ed9ng x\u00e1c \u0111\u1ecbnh ki\u1ec3u d\u1eef li\u1ec7u khi s\u1eed d\u1ee5ng h\u00e0m. B\u1ea1n c\u00f3 th\u1ec3 g\u1ecdi <\/span><span style=\"font-weight: 400;\">swapTwoValues<\/span><span style=\"font-weight: 400;\"> v\u1edbi <\/span><span style=\"font-weight: 400;\">Int<\/span><span style=\"font-weight: 400;\">, <\/span><span style=\"font-weight: 400;\">String<\/span><span style=\"font-weight: 400;\">, ho\u1eb7c b\u1ea5t k\u1ef3 ki\u1ec3u n\u00e0o kh\u00e1c.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">L\u1ee3i \u00edch c\u1ee7a vi\u1ec7c s\u1eed d\u1ee5ng <\/span><i><span style=\"font-weight: 400;\">Generics<\/span><\/i><span style=\"font-weight: 400;\">:<\/span><\/p>\n<ol>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">T\u00e1i s\u1eed d\u1ee5ng m\u00e3 (Code Reusability): Gi\u00fap vi\u1ebft c\u00e1c h\u00e0m v\u00e0 ki\u1ec3u d\u1eef li\u1ec7u c\u00f3 th\u1ec3 s\u1eed d\u1ee5ng cho nhi\u1ec1u ki\u1ec3u kh\u00e1c nhau, tr\u00e1nh ph\u1ea3i vi\u1ebft l\u1ea1i c\u00f9ng m\u1ed9t logic cho t\u1eebng ki\u1ec3u.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">An to\u00e0n v\u1ec1 ki\u1ec3u (Type Safety): Cho ph\u00e9p ki\u1ec3m tra l\u1ed7i li\u00ean quan \u0111\u1ebfn ki\u1ec3u d\u1eef li\u1ec7u ngay t\u1ea1i th\u1eddi \u0111i\u1ec3m bi\u00ean d\u1ecbch, gi\u00fap tr\u00e1nh l\u1ed7i runtime.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">D\u1ec5 b\u1ea3o tr\u00ec (Maintainability): V\u1edbi c\u00e1c \u0111o\u1ea1n m\u00e3 t\u1ed5ng qu\u00e1t v\u00e0 \u0111\u01a1n gi\u1ea3n h\u01a1n, b\u1ea1n c\u00f3 th\u1ec3 d\u1ec5 d\u00e0ng b\u1ea3o tr\u00ec v\u00e0 m\u1edf r\u1ed9ng code.<\/span><\/li>\n<\/ol>\n<h2><span class=\"ez-toc-section\" id=\"Cac_cau_hoi_phong_van_iOS_Developer_lien_quan_den_iOS_SDK\"><\/span><strong>C\u00e1c c\u00e2u h\u1ecfi ph\u1ecfng v\u1ea5n iOS Developer li\u00ean quan \u0111\u1ebfn iOS SDK<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n<h3><strong>Gi\u1ea3i th\u00edch v\u00f2ng \u0111\u1eddi c\u1ee7a m\u1ed9t UIViewController. C\u00e1c ph\u01b0\u01a1ng th\u1ee9c n\u00e0o \u0111\u01b0\u1ee3c g\u1ecdi khi view xu\u1ea5t hi\u1ec7n ho\u1eb7c bi\u1ebfn m\u1ea5t?<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">V\u00f2ng \u0111\u1eddi c\u1ee7a <\/span><span style=\"font-weight: 400;\">UIViewController<\/span><span style=\"font-weight: 400;\"> bao g\u1ed3m c\u00e1c ph\u01b0\u01a1ng th\u1ee9c qu\u1ea3n l\u00fd c\u00e1c giai \u0111o\u1ea1n khi view \u0111\u01b0\u1ee3c t\u1ea3i, hi\u1ec3n th\u1ecb, \u1ea9n, ho\u1eb7c h\u1ee7y. D\u01b0\u1edbi \u0111\u00e2y l\u00e0 c\u00e1c ph\u01b0\u01a1ng th\u1ee9c ch\u00ednh trong v\u00f2ng \u0111\u1eddi c\u1ee7a m\u1ed9t <\/span><span style=\"font-weight: 400;\">UIViewController<\/span><span style=\"font-weight: 400;\">:<\/span><\/p>\n<ol>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">viewDidLoad()<\/span><span style=\"font-weight: 400;\">: \u0110\u01b0\u1ee3c g\u1ecdi m\u1ed9t l\u1ea7n khi view controller t\u1ea3i xong view c\u1ee7a n\u00f3 v\u00e0o b\u1ed9 nh\u1edb. \u0110\u00e2y l\u00e0 n\u01a1i \u0111\u1ec3 c\u1ea5u h\u00ecnh c\u00e1c th\u00e0nh ph\u1ea7n UI v\u00e0 t\u1ea3i d\u1eef li\u1ec7u ban \u0111\u1ea7u.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">viewWillAppear(_:)<\/span><span style=\"font-weight: 400;\">: \u0110\u01b0\u1ee3c g\u1ecdi ngay tr\u01b0\u1edbc khi view s\u1eafp xu\u1ea5t hi\u1ec7n tr\u00ean m\u00e0n h\u00ecnh. Th\u01b0\u1eddng d\u00f9ng \u0111\u1ec3 c\u1eadp nh\u1eadt UI theo tr\u1ea1ng th\u00e1i m\u1edbi nh\u1ea5t ho\u1eb7c b\u1eaft \u0111\u1ea7u c\u00e1c ho\u1ea1t \u0111\u1ed9ng c\u1ea7n thi\u1ebft khi view hi\u1ec3n th\u1ecb (v\u00ed d\u1ee5: k\u00edch ho\u1ea1t c\u00e1c thay \u0111\u1ed5i d\u1eef li\u1ec7u t\u1eeb model).<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">viewDidAppear(_:)<\/span><span style=\"font-weight: 400;\">: \u0110\u01b0\u1ee3c g\u1ecdi ngay sau khi view \u0111\u00e3 xu\u1ea5t hi\u1ec7n tr\u00ean m\u00e0n h\u00ecnh. \u0110\u00e2y l\u00e0 n\u01a1i b\u1eaft \u0111\u1ea7u c\u00e1c t\u00e1c v\u1ee5 nh\u01b0 animation, l\u1ea5y d\u1eef li\u1ec7u theo th\u1eddi gian th\u1ef1c, ho\u1eb7c kh\u1edfi \u0111\u1ed9ng c\u00e1c timer.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">viewWillDisappear(_:)<\/span><span style=\"font-weight: 400;\">: \u0110\u01b0\u1ee3c g\u1ecdi ngay tr\u01b0\u1edbc khi view s\u1eafp b\u1ecb \u1ea9n kh\u1ecfi m\u00e0n h\u00ecnh. Th\u01b0\u1eddng d\u00f9ng \u0111\u1ec3 l\u01b0u d\u1eef li\u1ec7u, h\u1ee7y c\u00e1c t\u00e1c v\u1ee5 kh\u00f4ng c\u1ea7n thi\u1ebft, ho\u1eb7c d\u1eebng c\u00e1c hi\u1ec7u \u1ee9ng \u0111\u1ed9ng.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">viewDidDisappear(_:)<\/span><span style=\"font-weight: 400;\">: \u0110\u01b0\u1ee3c g\u1ecdi ngay sau khi view \u0111\u00e3 bi\u1ebfn m\u1ea5t kh\u1ecfi m\u00e0n h\u00ecnh. \u0110\u00e2y l\u00e0 n\u01a1i gi\u1ea3i ph\u00f3ng t\u00e0i nguy\u00ean ho\u1eb7c d\u1eebng c\u00e1c ho\u1ea1t \u0111\u1ed9ng kh\u00f4ng c\u1ea7n thi\u1ebft \u0111\u1ec3 ti\u1ebft ki\u1ec7m b\u1ed9 nh\u1edb.<\/span><\/li>\n<\/ol>\n<h3><strong>C\u00e1ch qu\u1ea3n l\u00fd b\u1ed9 nh\u1edb trong iOS l\u00e0 g\u00ec? Gi\u1ea3i th\u00edch ARC<\/strong><span style=\"font-weight: 400;\"><strong> (Automatic Reference Counting)<\/strong><\/span><\/h3>\n<p><span style=\"font-weight: 400;\">iOS s\u1eed d\u1ee5ng ARC (Automatic Reference Counting) \u0111\u1ec3 qu\u1ea3n l\u00fd b\u1ed9 nh\u1edb t\u1ef1 \u0111\u1ed9ng cho c\u00e1c \u0111\u1ed1i t\u01b0\u1ee3ng. ARC gi\u00fap theo d\u00f5i v\u00e0 qu\u1ea3n l\u00fd s\u1ed1 l\u01b0\u1ee3ng tham chi\u1ebfu \u0111\u1ebfn t\u1eebng \u0111\u1ed1i t\u01b0\u1ee3ng trong \u1ee9ng d\u1ee5ng v\u00e0 s\u1ebd gi\u1ea3i ph\u00f3ng b\u1ed9 nh\u1edb c\u1ee7a \u0111\u1ed1i t\u01b0\u1ee3ng khi kh\u00f4ng c\u00f2n tham chi\u1ebfu n\u00e0o \u0111\u1ebfn n\u00f3. ARC gi\u00fap \u0111\u1ea3m b\u1ea3o \u1ee9ng d\u1ee5ng s\u1eed d\u1ee5ng b\u1ed9 nh\u1edb hi\u1ec7u qu\u1ea3 m\u00e0 kh\u00f4ng c\u1ea7n gi\u1ea3i ph\u00f3ng b\u1ed9 nh\u1edb th\u1ee7 c\u00f4ng.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">C\u00e1ch th\u1ee9c ho\u1ea1t \u0111\u1ed9ng c\u1ee7a ARC:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Strong Reference: M\u1ed7i khi m\u1ed9t bi\u1ebfn ho\u1eb7c \u0111\u1ed1i t\u01b0\u1ee3ng c\u00f3 tham chi\u1ebfu <\/span><i><span style=\"font-weight: 400;\">m\u1ea1nh<\/span><\/i><span style=\"font-weight: 400;\"> (<\/span><span style=\"font-weight: 400;\">strong<\/span><span style=\"font-weight: 400;\">) \u0111\u1ebfn m\u1ed9t \u0111\u1ed1i t\u01b0\u1ee3ng, b\u1ed9 \u0111\u1ebfm tham chi\u1ebfu c\u1ee7a \u0111\u1ed1i t\u01b0\u1ee3ng \u0111\u00f3 t\u0103ng l\u00ean.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Deallocation: Khi b\u1ed9 \u0111\u1ebfm tham chi\u1ebfu c\u1ee7a \u0111\u1ed1i t\u01b0\u1ee3ng gi\u1ea3m v\u1ec1 0 (kh\u00f4ng c\u00f2n tham chi\u1ebfu n\u00e0o), ARC s\u1ebd t\u1ef1 \u0111\u1ed9ng gi\u1ea3i ph\u00f3ng b\u1ed9 nh\u1edb c\u1ee7a \u0111\u1ed1i t\u01b0\u1ee3ng \u0111\u00f3.<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">C\u00e1c lo\u1ea1i tham chi\u1ebfu trong ARC:<\/span><\/p>\n<ol>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Strong Reference: Gi\u1eef \u0111\u1ed1i t\u01b0\u1ee3ng trong b\u1ed9 nh\u1edb cho \u0111\u1ebfn khi kh\u00f4ng c\u00f2n tham chi\u1ebfu n\u00e0o.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Weak Reference: Kh\u00f4ng gi\u1eef \u0111\u1ed1i t\u01b0\u1ee3ng trong b\u1ed9 nh\u1edb; khi kh\u00f4ng c\u00f2n strong reference n\u00e0o, \u0111\u1ed1i t\u01b0\u1ee3ng s\u1ebd \u0111\u01b0\u1ee3c gi\u1ea3i ph\u00f3ng.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Unowned Reference: T\u01b0\u01a1ng t\u1ef1 <\/span><span style=\"font-weight: 400;\">weak<\/span><span style=\"font-weight: 400;\">, nh\u01b0ng ch\u1ec9 \u0111\u01b0\u1ee3c d\u00f9ng khi bi\u1ebft ch\u1eafc ch\u1eafn r\u1eb1ng \u0111\u1ed1i t\u01b0\u1ee3ng s\u1ebd lu\u00f4n t\u1ed3n t\u1ea1i trong su\u1ed1t v\u00f2ng \u0111\u1eddi c\u1ee7a unowned reference (tr\u00e1nh c\u00e1c tr\u01b0\u1eddng h\u1ee3p b\u1ecb g\u00e1n th\u00e0nh <\/span><span style=\"font-weight: 400;\">nil<\/span><span style=\"font-weight: 400;\">).<\/span><\/li>\n<\/ol>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-81599\" src=\"https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/11\/cau-hoi-phong-van-ios-developer-1-vippro.png\" alt=\"c\u00e2u h\u1ecfi ph\u1ecfng v\u1ea5n ios developer - itviec blog\" width=\"1393\" height=\"822\" srcset=\"https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/11\/cau-hoi-phong-van-ios-developer-1-vippro.png 1393w, https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/11\/cau-hoi-phong-van-ios-developer-1-vippro-300x177.png 300w, https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/11\/cau-hoi-phong-van-ios-developer-1-vippro-700x413.png 640w, https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/11\/cau-hoi-phong-van-ios-developer-1-vippro-200x118.png 200w, https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/11\/cau-hoi-phong-van-ios-developer-1-vippro-100x59.png 100w\" sizes=\"auto, (max-width: 1393px) 100vw, 1393px\" \/><\/p>\n<p><span style=\"font-weight: 400;\">Tr\u00ean \u0111\u00e2y l\u00e0 h\u00ecnh minh ho\u1ea1 v\u1ec1 c\u01a1 ch\u1ebf qu\u1ea3n l\u00fd b\u1ed9 nh\u1edb trong iOS.<\/span><\/p>\n<h3><strong>Delegate v\u00e0 Closure trong Swift kh\u00e1c nhau nh\u01b0 th\u1ebf n\u00e0o? Khi n\u00e0o n\u00ean s\u1eed d\u1ee5ng t\u1eebng lo\u1ea1i?<\/strong><\/h3>\n<table>\n<tbody>\n<tr>\n<td><span style=\"font-weight: 400;\">Thu\u1ed9c t\u00ednh\u00a0<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Delegate<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Closure<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">\u0110\u1ecbnh ngh\u0129a\u00a0<\/span><\/td>\n<td><span style=\"font-weight: 400;\">M\u1ed9t thi\u1ebft k\u1ebf h\u01b0\u1edbng \u0111\u1ed1i t\u01b0\u1ee3ng, cho ph\u00e9p m\u1ed9t \u0111\u1ed1i t\u01b0\u1ee3ng giao nhi\u1ec7m v\u1ee5 cho \u0111\u1ed1i t\u01b0\u1ee3ng kh\u00e1c.<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Kh\u1ed1i m\u00e3 kh\u00f4ng c\u00f3 t\u00ean, c\u00f3 th\u1ec3 l\u01b0u tr\u1eef v\u00e0 truy\u1ec1n qua c\u00e1c h\u00e0m nh\u01b0 m\u1ed9t tham s\u1ed1.<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">C\u00e1ch s\u1eed d\u1ee5ng<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Th\u01b0\u1eddng l\u00e0 m\u1ed9t protocol c\u00f3 c\u00e1c ph\u01b0\u01a1ng th\u1ee9c \u0111\u01b0\u1ee3c g\u1ecdi b\u1edfi \u0111\u1ed1i t\u01b0\u1ee3ng kh\u00e1c \u0111\u1ec3 ph\u1ea3n h\u1ed3i c\u00e1c s\u1ef1 ki\u1ec7n ho\u1eb7c t\u01b0\u01a1ng t\u00e1c.<\/span><\/td>\n<td><span style=\"font-weight: 400;\">\u0110\u01b0\u1ee3c truy\u1ec1n tr\u1ef1c ti\u1ebfp \u0111\u1ec3 x\u1eed l\u00fd c\u00e1c t\u00e1c v\u1ee5 \u0111\u01a1n gi\u1ea3n, tr\u1ea3 v\u1ec1 k\u1ebft qu\u1ea3 ho\u1eb7c th\u1ef1c hi\u1ec7n h\u00e0nh \u0111\u1ed9ng ng\u1eafn g\u1ecdn.<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">T\u00ednh m\u1edf r\u1ed9ng<\/span><\/td>\n<td><span style=\"font-weight: 400;\">T\u1ea1o m\u1ed1i quan h\u1ec7 r\u00f5 r\u00e0ng v\u00e0 l\u00e2u d\u00e0i gi\u1eefa hai \u0111\u1ed1i t\u01b0\u1ee3ng, th\u00edch h\u1ee3p cho c\u00e1c giao di\u1ec7n ph\u1ee9c t\u1ea1p ho\u1eb7c c\u00e1c l\u1edbp c\u1ea7n giao ti\u1ebfp hai chi\u1ec1u.<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Ph\u00f9 h\u1ee3p v\u1edbi c\u00e1c t\u00e1c v\u1ee5 ng\u1eafn g\u1ecdn, kh\u00f4ng y\u00eau c\u1ea7u m\u1ed1i quan h\u1ec7 l\u00e2u d\u00e0i gi\u1eefa c\u00e1c \u0111\u1ed1i t\u01b0\u1ee3ng.<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p><span style=\"font-weight: 400;\">Khi n\u00e0o s\u1eed d\u1ee5ng t\u1eebng lo\u1ea1i:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Delegate: S\u1eed d\u1ee5ng khi c\u1ea7n giao ti\u1ebfp ph\u1ee9c t\u1ea1p v\u00e0 li\u00ean t\u1ee5c gi\u1eefa hai \u0111\u1ed1i t\u01b0\u1ee3ng, \u0111\u1eb7c bi\u1ec7t khi m\u1ed9t \u0111\u1ed1i t\u01b0\u1ee3ng c\u1ea7n ph\u1ea3n h\u1ed3i nhi\u1ec1u s\u1ef1 ki\u1ec7n kh\u00e1c nhau. Th\u00edch h\u1ee3p cho c\u00e1c tr\u01b0\u1eddng h\u1ee3p nh\u01b0 \u0111i\u1ec1u khi\u1ec3n UI, n\u01a1i m\u1ed9t controller c\u1ea7n nh\u1eadn th\u00f4ng b\u00e1o t\u1eeb view (nh\u01b0 <\/span><span style=\"font-weight: 400;\">UITableViewDelegate<\/span><span style=\"font-weight: 400;\">).<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Closure: S\u1eed d\u1ee5ng cho c\u00e1c t\u00e1c v\u1ee5 ng\u1eafn h\u1ea1n ho\u1eb7c \u0111\u01a1n gi\u1ea3n, n\u01a1i b\u1ea1n c\u1ea7n truy\u1ec1n m\u1ed9t kh\u1ed1i m\u00e3 \u0111\u1ec3 th\u1ef1c hi\u1ec7n m\u1ed9t l\u1ea7n, ch\u1eb3ng h\u1ea1n nh\u01b0 x\u1eed l\u00fd k\u1ebft qu\u1ea3 t\u1eeb m\u1ed9t API call, animation completion, ho\u1eb7c x\u1eed l\u00fd t\u00e1c v\u1ee5 kh\u00f4ng \u0111\u1ed3ng b\u1ed9.<\/span><\/li>\n<\/ul>\n<h3><strong>NotificationCenter l\u00e0 g\u00ec v\u00e0 khi n\u00e0o n\u00ean s\u1eed d\u1ee5ng?<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">NotificationCenter<\/span><span style=\"font-weight: 400;\"> trong iOS l\u00e0 m\u1ed9t c\u01a1 ch\u1ebf cung c\u1ea5p c\u00e1ch th\u1ee9c \u0111\u1ec3 truy\u1ec1n th\u00f4ng tin gi\u1eefa c\u00e1c \u0111\u1ed1i t\u01b0\u1ee3ng m\u00e0 kh\u00f4ng c\u1ea7n t\u1ea1o m\u1ed1i li\u00ean k\u1ebft tr\u1ef1c ti\u1ebfp gi\u1eefa ch\u00fang. V\u1edbi <\/span><i><span style=\"font-weight: 400;\">NotificationCenter<\/span><\/i><span style=\"font-weight: 400;\">, m\u1ed9t \u0111\u1ed1i t\u01b0\u1ee3ng c\u00f3 th\u1ec3 &#8220;post&#8221; (g\u1eedi) m\u1ed9t th\u00f4ng b\u00e1o, v\u00e0 c\u00e1c \u0111\u1ed1i t\u01b0\u1ee3ng kh\u00e1c c\u00f3 th\u1ec3 &#8220;observe&#8221; (quan s\u00e1t) v\u00e0 ph\u1ea3n h\u1ed3i khi th\u00f4ng b\u00e1o \u0111\u00f3 \u0111\u01b0\u1ee3c ph\u00e1t \u0111i. \u0110i\u1ec1u n\u00e0y gi\u00fap gi\u1ea3m ph\u1ee5 thu\u1ed9c gi\u1eefa c\u00e1c \u0111\u1ed1i t\u01b0\u1ee3ng, t\u0103ng t\u00ednh linh ho\u1ea1t v\u00e0 kh\u1ea3 n\u0103ng m\u1edf r\u1ed9ng c\u1ee7a \u1ee9ng d\u1ee5ng.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">C\u00e1ch s\u1eed d\u1ee5ng:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">\u0110\u0103ng k\u00fd m\u1ed9t \u0111\u1ed1i t\u01b0\u1ee3ng \u0111\u1ec3 quan s\u00e1t m\u1ed9t th\u00f4ng b\u00e1o: S\u1eed d\u1ee5ng ph\u01b0\u01a1ng th\u1ee9c <\/span><span style=\"font-weight: 400;\">addObserver(_:selector:name:object:)<\/span><span style=\"font-weight: 400;\">.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">G\u1eedi (post) m\u1ed9t th\u00f4ng b\u00e1o: S\u1eed d\u1ee5ng <\/span><span style=\"font-weight: 400;\">post(name:object:userInfo:)<\/span><span style=\"font-weight: 400;\"> \u0111\u1ec3 ph\u00e1t \u0111i th\u00f4ng b\u00e1o.<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">Khi n\u00e0o n\u00ean s\u1eed d\u1ee5ng <\/span><i><span style=\"font-weight: 400;\">NotificationCenter<\/span><\/i><span style=\"font-weight: 400;\">:<\/span><\/p>\n<ol>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Truy\u1ec1n th\u00f4ng gi\u1eefa c\u00e1c th\u00e0nh ph\u1ea7n kh\u00f4ng c\u00f3 m\u1ed1i li\u00ean k\u1ebft tr\u1ef1c ti\u1ebfp: Khi c\u1ea7n truy\u1ec1n d\u1eef li\u1ec7u ho\u1eb7c th\u00f4ng b\u00e1o s\u1ef1 ki\u1ec7n gi\u1eefa c\u00e1c l\u1edbp ho\u1eb7c module kh\u00f4ng c\u00f3 m\u1ed1i quan h\u1ec7 tr\u1ef1c ti\u1ebfp.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">C\u1eadp nh\u1eadt nhi\u1ec1u \u0111\u1ed1i t\u01b0\u1ee3ng khi c\u00f3 s\u1ef1 ki\u1ec7n x\u1ea3y ra: Khi m\u1ed9t s\u1ef1 ki\u1ec7n (nh\u01b0 thay \u0111\u1ed5i d\u1eef li\u1ec7u, thay \u0111\u1ed5i tr\u1ea1ng th\u00e1i m\u1ea1ng) x\u1ea3y ra v\u00e0 c\u1ea7n th\u00f4ng b\u00e1o \u0111\u1ebfn nhi\u1ec1u \u0111\u1ed1i t\u01b0\u1ee3ng c\u00f9ng l\u00fac m\u00e0 kh\u00f4ng c\u1ea7n ph\u1ea3i gi\u1eef tham chi\u1ebfu \u0111\u1ebfn t\u1eebng \u0111\u1ed1i t\u01b0\u1ee3ng \u0111\u00f3.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Gi\u1ea3m ph\u1ee5 thu\u1ed9c (Loosely Coupling): S\u1eed d\u1ee5ng <\/span><i><span style=\"font-weight: 400;\">NotificationCenter<\/span><\/i><span style=\"font-weight: 400;\"> gi\u00fap gi\u1ea3m \u0111\u1ed9 ph\u1ee5 thu\u1ed9c gi\u1eefa c\u00e1c l\u1edbp, c\u1ea3i thi\u1ec7n kh\u1ea3 n\u0103ng b\u1ea3o tr\u00ec v\u00e0 t\u00e1i s\u1eed d\u1ee5ng m\u00e3.<\/span><\/li>\n<\/ol>\n<p><span style=\"font-weight: 400;\">V\u00ed d\u1ee5 s\u1eed d\u1ee5ng Notification Center:<\/span><\/p>\n<pre><span style=\"font-weight: 400;\">import UIKit<\/span>\r\n\r\n<span style=\"font-weight: 400;\">class LoginViewController: UIViewController {<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0func loginUser() {<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\/\/ Gi\u1ea3 s\u1eed ng\u01b0\u1eddi d\u00f9ng \u0111\u00e3 \u0111\u0103ng nh\u1eadp th\u00e0nh c\u00f4ng<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0print(\"User logged in successfully\")<\/span>\r\n\r\n<span style=\"font-weight: 400;\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\/\/ G\u1eedi th\u00f4ng b\u00e1o \"UserDidLogin\"<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0NotificationCenter.default.post(name: Notification.Name(\"UserDidLogin\"), object: nil)<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0}<\/span>\r\n<span style=\"font-weight: 400;\">}<\/span><\/pre>\n<p><span style=\"font-weight: 400;\">Trong l\u1edbp <\/span><span style=\"font-weight: 400;\">LoginViewController<\/span><span style=\"font-weight: 400;\">, sau khi ng\u01b0\u1eddi d\u00f9ng \u0111\u0103ng nh\u1eadp th\u00e0nh c\u00f4ng, g\u1eedi th\u00f4ng b\u00e1o b\u1eb1ng c\u00e1ch d\u00f9ng <\/span><span style=\"font-weight: 400;\">NotificationCenter<\/span><span style=\"font-weight: 400;\">.<\/span><\/p>\n<pre><span style=\"font-weight: 400;\">import UIKit<\/span>\r\n\r\n<span style=\"font-weight: 400;\">class HomeViewController: UIViewController {<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0override func viewDidLoad() {<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0super.viewDidLoad()<\/span>\r\n\r\n<span style=\"font-weight: 400;\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\/\/ \u0110\u0103ng k\u00fd l\u1eafng nghe th\u00f4ng b\u00e1o \"UserDidLogin\"<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0NotificationCenter.default.addObserver(self, selector: #selector(userDidLogin), name: Notification.Name(\"UserDidLogin\"), object: nil)<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0}<\/span>\r\n\r\n<span style=\"font-weight: 400;\">\u00a0\u00a0\u00a0\u00a0\/\/ Ph\u01b0\u01a1ng th\u1ee9c s\u1ebd \u0111\u01b0\u1ee3c g\u1ecdi khi nh\u1eadn th\u00f4ng b\u00e1o<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0@objc func userDidLogin() {<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0print(\"Notification received: User logged in\")<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\/\/ C\u1eadp nh\u1eadt giao di\u1ec7n, t\u1ea3i d\u1eef li\u1ec7u, ho\u1eb7c th\u1ef1c hi\u1ec7n c\u00e1c h\u00e0nh \u0111\u1ed9ng c\u1ea7n thi\u1ebft<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0}<\/span>\r\n\r\n<span style=\"font-weight: 400;\">\u00a0\u00a0\u00a0\u00a0deinit {<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0NotificationCenter.default.removeObserver(self, name: Notification.Name(\"UserDidLogin\"), object: nil)<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0}<\/span>\r\n<span style=\"font-weight: 400;\">}<\/span><\/pre>\n<p><span style=\"font-weight: 400;\">Gi\u1ea3i th\u00edch:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">\u0110\u0103ng th\u00f4ng b\u00e1o: Sau khi \u0111\u0103ng nh\u1eadp, <\/span><span style=\"font-weight: 400;\">LoginViewController<\/span><span style=\"font-weight: 400;\"> g\u1eedi th\u00f4ng b\u00e1o &#8220;UserDidLogin&#8221; \u0111\u1ec3 b\u00e1o cho c\u00e1c l\u1edbp kh\u00e1c r\u1eb1ng qu\u00e1 tr\u00ecnh \u0111\u0103ng nh\u1eadp \u0111\u00e3 ho\u00e0n t\u1ea5t.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">L\u1eafng nghe th\u00f4ng b\u00e1o: <\/span><span style=\"font-weight: 400;\">HomeViewController<\/span><span style=\"font-weight: 400;\"> \u0111\u0103ng k\u00fd \u0111\u1ec3 l\u1eafng nghe th\u00f4ng b\u00e1o &#8220;UserDidLogin&#8221; v\u00e0 g\u1ecdi ph\u01b0\u01a1ng th\u1ee9c <\/span><span style=\"font-weight: 400;\">userDidLogin<\/span><span style=\"font-weight: 400;\"> khi nh\u1eadn \u0111\u01b0\u1ee3c th\u00f4ng b\u00e1o, gi\u00fap n\u00f3 th\u1ef1c hi\u1ec7n c\u00e1c h\u00e0nh \u0111\u1ed9ng li\u00ean quan, ch\u1eb3ng h\u1ea1n nh\u01b0 c\u1eadp nh\u1eadt UI.<\/span><\/li>\n<\/ul>\n<h3><strong>Ph\u00e2n bi\u1ec7t gi\u1eefa frame v\u00e0 bounds c\u1ee7a m\u1ed9t UIView<\/strong><\/h3>\n<table>\n<tbody>\n<tr>\n<td><span style=\"font-weight: 400;\">Thu\u1ed9c t\u00ednh\u00a0<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Frame<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Bounds<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">\u0110\u1ecbnh ngh\u0129a\u00a0<\/span><\/td>\n<td><span style=\"font-weight: 400;\">X\u00e1c \u0111\u1ecbnh v\u1ecb tr\u00ed v\u00e0 k\u00edch th\u01b0\u1edbc c\u1ee7a <\/span><span style=\"font-weight: 400;\">UIView<\/span><span style=\"font-weight: 400;\"> trong h\u1ec7 t\u1ecda \u0111\u1ed9 c\u1ee7a <\/span><span style=\"font-weight: 400;\">superview<\/span><span style=\"font-weight: 400;\"> (view cha).<\/span><\/td>\n<td><span style=\"font-weight: 400;\">X\u00e1c \u0111\u1ecbnh v\u1ecb tr\u00ed v\u00e0 k\u00edch th\u01b0\u1edbc c\u1ee7a <\/span><span style=\"font-weight: 400;\">UIView<\/span><span style=\"font-weight: 400;\"> trong ch\u00ednh h\u1ec7 t\u1ecda \u0111\u1ed9 c\u1ee7a n\u00f3.<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">H\u1ec7 to\u1ea1 \u0111\u1ed9\u00a0<\/span><\/td>\n<td><span style=\"font-weight: 400;\">H\u1ec7 t\u1ecda \u0111\u1ed9 c\u1ee7a <\/span><span style=\"font-weight: 400;\">superview<\/span><span style=\"font-weight: 400;\"> (view cha).<\/span><\/td>\n<td><span style=\"font-weight: 400;\">H\u1ec7 t\u1ecda \u0111\u1ed9 n\u1ed9i b\u1ed9 c\u1ee7a <\/span><span style=\"font-weight: 400;\">UIView<\/span><span style=\"font-weight: 400;\"> (0,0 \u1edf g\u00f3c tr\u00ean b\u00ean tr\u00e1i).<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">Thay \u0111\u1ed5i v\u1ecb tr\u00ed<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Thay \u0111\u1ed5i <\/span><span style=\"font-weight: 400;\">frame.origin<\/span><span style=\"font-weight: 400;\"> s\u1ebd di chuy\u1ec3n <\/span><span style=\"font-weight: 400;\">UIView<\/span><span style=\"font-weight: 400;\"> trong <\/span><span style=\"font-weight: 400;\">superview<\/span><span style=\"font-weight: 400;\">.<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Thay \u0111\u1ed5i <\/span><span style=\"font-weight: 400;\">bounds.origin<\/span><span style=\"font-weight: 400;\"> s\u1ebd di chuy\u1ec3n n\u1ed9i dung b\u00ean trong <\/span><span style=\"font-weight: 400;\">UIView<\/span><span style=\"font-weight: 400;\"> m\u00e0 kh\u00f4ng \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn v\u1ecb tr\u00ed c\u1ee7a n\u00f3 trong <\/span><span style=\"font-weight: 400;\">superview<\/span><span style=\"font-weight: 400;\">.<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">\u1ee8ng d\u1ee5ng ch\u00ednh<\/span><\/td>\n<td><span style=\"font-weight: 400;\">D\u00f9ng \u0111\u1ec3 \u0111\u1ecbnh v\u1ecb <\/span><span style=\"font-weight: 400;\">UIView<\/span><span style=\"font-weight: 400;\"> trong <\/span><span style=\"font-weight: 400;\">superview<\/span><span style=\"font-weight: 400;\">.<\/span><\/td>\n<td><span style=\"font-weight: 400;\">D\u00f9ng \u0111\u1ec3 cu\u1ed9n ho\u1eb7c c\u1eaft n\u1ed9i dung c\u1ee7a ch\u00ednh <\/span><span style=\"font-weight: 400;\">UIView<\/span><span style=\"font-weight: 400;\"> t\u1eeb b\u00ean trong.<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-81600\" src=\"https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/11\/cau-hoi-phong-van-ios-developer-2-vippro.jpg\" alt=\"c\u00e2u h\u1ecfi ph\u1ecfng v\u1ea5n ios developer - itviec blog\" width=\"800\" height=\"562\" srcset=\"https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/11\/cau-hoi-phong-van-ios-developer-2-vippro.jpg 800w, https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/11\/cau-hoi-phong-van-ios-developer-2-vippro-300x211.jpg 300w, https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/11\/cau-hoi-phong-van-ios-developer-2-vippro-641x450.jpg 640w, https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/11\/cau-hoi-phong-van-ios-developer-2-vippro-200x141.jpg 200w, https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/11\/cau-hoi-phong-van-ios-developer-2-vippro-100x70.jpg 100w\" sizes=\"auto, (max-width: 800px) 100vw, 800px\" \/><\/p>\n<p><span style=\"font-weight: 400;\">H\u00ecnh \u1ea3nh tr\u00ean mi\u00eau t\u1ea3 c\u00e1ch s\u1eed d\u1ee5ng kh\u00e1c nhau trong giao di\u1ec7n di \u0111\u1ed9ng c\u1ee7a Frame v\u00e0 Bounds.<\/span><\/p>\n<h3><strong>Core Data l\u00e0 g\u00ec? Khi n\u00e0o n\u00ean s\u1eed d\u1ee5ng Core Data so v\u1edbi c\u00e1c t\u00f9y ch\u1ecdn l\u01b0u tr\u1eef d\u1eef li\u1ec7u kh\u00e1c?<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">Core Data<\/span><span style=\"font-weight: 400;\"> l\u00e0 m\u1ed9t framework qu\u1ea3n l\u00fd d\u1eef li\u1ec7u trong iOS \u0111\u01b0\u1ee3c Apple cung c\u1ea5p, cho ph\u00e9p l\u01b0u tr\u1eef, truy v\u1ea5n v\u00e0 qu\u1ea3n l\u00fd d\u1eef li\u1ec7u c\u1ee5c b\u1ed9 d\u01b0\u1edbi d\u1ea1ng c\u00e1c \u0111\u1ed1i t\u01b0\u1ee3ng. Core Data h\u1ed7 tr\u1ee3 m\u00f4 h\u00ecnh h\u00f3a d\u1eef li\u1ec7u quan h\u1ec7 v\u00e0 \u0111i k\u00e8m v\u1edbi c\u00e1c t\u00ednh n\u0103ng nh\u01b0 t\u1ef1 \u0111\u1ed9ng l\u01b0u tr\u1eef, truy v\u1ea5n, v\u00e0 t\u1ed1i \u01b0u h\u00f3a b\u1ed9 nh\u1edb.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Khi n\u00e0o n\u00ean s\u1eed d\u1ee5ng Core Data:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Khi c\u1ea7n qu\u1ea3n l\u00fd d\u1eef li\u1ec7u ph\u1ee9c t\u1ea1p: Core Data r\u1ea5t h\u1eefu \u00edch cho c\u00e1c \u1ee9ng d\u1ee5ng c\u1ea7n l\u01b0u tr\u1eef v\u00e0 x\u1eed l\u00fd l\u01b0\u1ee3ng l\u1edbn d\u1eef li\u1ec7u c\u00f3 quan h\u1ec7 ph\u1ee9c t\u1ea1p gi\u1eefa c\u00e1c th\u1ef1c th\u1ec3, ch\u1eb3ng h\u1ea1n nh\u01b0 \u1ee9ng d\u1ee5ng qu\u1ea3n l\u00fd ghi ch\u00fa, l\u1ecbch, hay qu\u1ea3n l\u00fd t\u00e0i ch\u00ednh.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Khi c\u1ea7n hi\u1ec7u su\u1ea5t cao: Core Data t\u1ed1i \u01b0u h\u00f3a vi\u1ec7c truy v\u1ea5n v\u00e0 qu\u1ea3n l\u00fd b\u1ed9 nh\u1edb th\u00f4ng qua t\u00ednh n\u0103ng lazy loading v\u00e0 caching, gi\u00fap hi\u1ec7u su\u1ea5t \u1ee9ng d\u1ee5ng \u1ed5n \u0111\u1ecbnh ngay c\u1ea3 v\u1edbi l\u01b0\u1ee3ng d\u1eef li\u1ec7u l\u1edbn.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Khi c\u1ea7n h\u1ed7 tr\u1ee3 undo\/redo: Core Data c\u00f3 s\u1eb5n t\u00ednh n\u0103ng undo\/redo cho ph\u00e9p ng\u01b0\u1eddi d\u00f9ng quay l\u1ea1i ho\u1eb7c l\u1eb7p l\u1ea1i c\u00e1c thay \u0111\u1ed5i d\u1ec5 d\u00e0ng.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Khi c\u1ea7n theo d\u00f5i v\u00e0 l\u01b0u tr\u1eef tr\u1ea1ng th\u00e1i: Core Data h\u1ed7 tr\u1ee3 theo d\u00f5i tr\u1ea1ng th\u00e1i c\u1ee7a c\u00e1c \u0111\u1ed1i t\u01b0\u1ee3ng, r\u1ea5t ph\u00f9 h\u1ee3p cho c\u00e1c \u1ee9ng d\u1ee5ng y\u00eau c\u1ea7u theo d\u00f5i s\u1ef1 thay \u0111\u1ed5i v\u00e0 \u0111\u1ed3ng b\u1ed9 d\u1eef li\u1ec7u li\u00ean t\u1ee5c.<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">So s\u00e1nh v\u1edbi c\u00e1c t\u00f9y ch\u1ecdn l\u01b0u tr\u1eef kh\u00e1c:<\/span><\/p>\n<table>\n<tbody>\n<tr>\n<td><strong>T\u00f9y ch\u1ecdn l\u01b0u tr\u1eef<\/strong><\/td>\n<td><strong>T\u00ecnh hu\u1ed1ng s\u1eed d\u1ee5ng<\/strong><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">Core Data<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Khi c\u1ea7n qu\u1ea3n l\u00fd d\u1eef li\u1ec7u ph\u1ee9c t\u1ea1p, t\u1ed1i \u01b0u h\u00f3a truy v\u1ea5n, v\u00e0 c\u00f3 m\u1ed1i quan h\u1ec7 gi\u1eefa c\u00e1c \u0111\u1ed1i t\u01b0\u1ee3ng.<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">UserDefaults<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Khi l\u01b0u tr\u1eef d\u1eef li\u1ec7u nh\u1ecf, kh\u00f4ng ph\u1ee9c t\u1ea1p, ch\u1eb3ng h\u1ea1n nh\u01b0 c\u00e0i \u0111\u1eb7t, t\u00f9y ch\u1ecdn ng\u01b0\u1eddi d\u00f9ng.<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">Keychain<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Khi c\u1ea7n l\u01b0u tr\u1eef d\u1eef li\u1ec7u b\u1ea3o m\u1eadt nh\u01b0 token, m\u1eadt kh\u1ea9u.<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">File Storage<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Khi l\u01b0u tr\u1eef t\u1ec7p tin, h\u00ecnh \u1ea3nh ho\u1eb7c d\u1eef li\u1ec7u kh\u00f4ng quan h\u1ec7 (kh\u00f4ng c\u1ea7n truy v\u1ea5n).<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">SQLite<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Khi c\u1ea7n c\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7 \u0111\u01a1n gi\u1ea3n m\u00e0 kh\u00f4ng c\u1ea7n t\u00ednh n\u0103ng qu\u1ea3n l\u00fd \u0111\u1ed1i t\u01b0\u1ee3ng c\u1ee7a Core Data.<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h3><strong>URLSession l\u00e0 g\u00ec v\u00e0 l\u00e0m th\u1ebf n\u00e0o \u0111\u1ec3 th\u1ef1c hi\u1ec7n m\u1ed9t y\u00eau c\u1ea7u m\u1ea1ng?<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">URLSession<\/span><span style=\"font-weight: 400;\"> l\u00e0 m\u1ed9t API trong Swift cho ph\u00e9p \u1ee9ng d\u1ee5ng giao ti\u1ebfp v\u1edbi m\u1ea1ng, th\u1ef1c hi\u1ec7n c\u00e1c t\u00e1c v\u1ee5 nh\u01b0 t\u1ea3i d\u1eef li\u1ec7u, t\u1ea3i file, ho\u1eb7c t\u1ea3i l\u00ean d\u1eef li\u1ec7u. URLSession cung c\u1ea5p c\u00e1c ph\u01b0\u01a1ng th\u1ee9c \u0111\u1ed3ng b\u1ed9 v\u00e0 kh\u00f4ng \u0111\u1ed3ng b\u1ed9 \u0111\u1ec3 th\u1ef1c hi\u1ec7n c\u00e1c y\u00eau c\u1ea7u HTTP ho\u1eb7c HTTPS.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">C\u00e1ch th\u1ef1c hi\u1ec7n m\u1ed9t y\u00eau c\u1ea7u m\u1ea1ng v\u1edbi URLSession:<\/span><\/p>\n<ol>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">T\u1ea1o URL: X\u00e1c \u0111\u1ecbnh URL c\u1ee7a y\u00eau c\u1ea7u.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">T\u1ea1o URLSession: S\u1eed d\u1ee5ng <\/span><span style=\"font-weight: 400;\">URLSession.shared<\/span><span style=\"font-weight: 400;\"> cho c\u00e1c t\u00e1c v\u1ee5 \u0111\u01a1n gi\u1ea3n ho\u1eb7c c\u1ea5u h\u00ecnh ri\u00eang b\u1eb1ng c\u00e1ch t\u1ea1o <\/span><span style=\"font-weight: 400;\">URLSessionConfiguration<\/span><span style=\"font-weight: 400;\">.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">T\u1ea1o y\u00eau c\u1ea7u (Request): T\u1ea1o m\u1ed9t y\u00eau c\u1ea7u v\u1edbi ph\u01b0\u01a1ng th\u1ee9c v\u00e0 c\u00e1c tham s\u1ed1 c\u1ea7n thi\u1ebft.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">T\u1ea1o task: S\u1eed d\u1ee5ng <\/span><span style=\"font-weight: 400;\">dataTask<\/span><span style=\"font-weight: 400;\"> \u0111\u1ec3 g\u1eedi y\u00eau c\u1ea7u v\u00e0 x\u1eed l\u00fd ph\u1ea3n h\u1ed3i.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Th\u1ef1c thi task: G\u1ecdi <\/span><span style=\"font-weight: 400;\">task.resume()<\/span><span style=\"font-weight: 400;\"> \u0111\u1ec3 b\u1eaft \u0111\u1ea7u y\u00eau c\u1ea7u.<\/span><\/li>\n<\/ol>\n<p><span style=\"font-weight: 400;\">V\u00ed d\u1ee5:<\/span><\/p>\n<pre><span style=\"font-weight: 400;\">import Foundation<\/span>\r\n\r\n<span style=\"font-weight: 400;\">func fetchData() {<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\/\/ 1. T\u1ea1o URL<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0guard let url = URL(string: \"https:\/\/jsonplaceholder.typicode.com\/posts\") else { return }<\/span>\r\n\r\n<span style=\"font-weight: 400;\">\u00a0\u00a0\u00a0\u00a0\/\/ 2. T\u1ea1o URLSession<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0let session = URLSession.shared<\/span>\r\n\r\n<span style=\"font-weight: 400;\">\u00a0\u00a0\u00a0\u00a0\/\/ 3. T\u1ea1o task<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0let task = session.dataTask(with: url) { data, response, error in<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\/\/ Ki\u1ec3m tra l\u1ed7i<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0if let error = error {<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0print(\"Error: \\(error.localizedDescription)\")<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0return<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0}<\/span>\r\n\r\n<span style=\"font-weight: 400;\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\/\/ Ki\u1ec3m tra d\u1eef li\u1ec7u v\u00e0 ph\u1ea3n h\u1ed3i<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0guard let data = data, let response = response as? HTTPURLResponse, response.statusCode == 200 else {<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0print(\"No data or status code error\")<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0return<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0}<\/span>\r\n\r\n<span style=\"font-weight: 400;\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\/\/ X\u1eed l\u00fd d\u1eef li\u1ec7u JSON<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0do {<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0if let json = try JSONSerialization.jsonObject(with: data, options: []) as? [[String: Any]] {<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0print(\"Received JSON: \\(json)\")<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0}<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0} catch {<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0print(\"JSON decoding error: \\(error.localizedDescription)\")<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0}<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0}<\/span>\r\n\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\/\/ 4. Th\u1ef1c thi task<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0task.resume()<\/span>\r\n<span style=\"font-weight: 400;\">}<\/span><\/pre>\n<p><span style=\"font-weight: 400;\">Gi\u1ea3i th\u00edch:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">URLSession.shared: T\u1ea1o m\u1ed9t phi\u00ean m\u1eb7c \u0111\u1ecbnh cho c\u00e1c t\u00e1c v\u1ee5 \u0111\u01a1n gi\u1ea3n.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">dataTask(with:): T\u1ea1o m\u1ed9t <\/span><i><span style=\"font-weight: 400;\">data task<\/span><\/i><span style=\"font-weight: 400;\"> \u0111\u1ec3 th\u1ef1c hi\u1ec7n y\u00eau c\u1ea7u GET.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">task.resume(): B\u1eaft \u0111\u1ea7u th\u1ef1c thi y\u00eau c\u1ea7u.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">X\u1eed l\u00fd JSON: S\u1eed d\u1ee5ng <\/span><span style=\"font-weight: 400;\">JSONSerialization<\/span><span style=\"font-weight: 400;\"> \u0111\u1ec3 gi\u1ea3i m\u00e3 d\u1eef li\u1ec7u JSON.<\/span><\/li>\n<\/ul>\n<h3><strong>GCD (Grand Central Dispatch) l\u00e0 g\u00ec? C\u00e1ch s\u1eed d\u1ee5ng DispatchQueue \u0111\u1ec3 th\u1ef1c hi\u1ec7n c\u00f4ng vi\u1ec7c b\u1ea5t \u0111\u1ed3ng b\u1ed9?<\/strong><\/h3>\n<p><i><span style=\"font-weight: 400;\">GCD (Grand Central Dispatch)<\/span><\/i><span style=\"font-weight: 400;\"> l\u00e0 m\u1ed9t framework trong iOS v\u00e0 macOS gi\u00fap qu\u1ea3n l\u00fd c\u00e1c t\u00e1c v\u1ee5 tr\u00ean nhi\u1ec1u lu\u1ed3ng m\u1ed9t c\u00e1ch hi\u1ec7u qu\u1ea3, cho ph\u00e9p th\u1ef1c hi\u1ec7n c\u00e1c c\u00f4ng vi\u1ec7c b\u1ea5t \u0111\u1ed3ng b\u1ed9 v\u00e0 t\u1ed1i \u01b0u h\u00f3a t\u00e0i nguy\u00ean h\u1ec7 th\u1ed1ng. V\u1edbi GCD, b\u1ea1n c\u00f3 th\u1ec3 tr\u00e1nh kh\u00f3a giao di\u1ec7n ng\u01b0\u1eddi d\u00f9ng khi x\u1eed l\u00fd c\u00e1c t\u00e1c v\u1ee5 n\u1eb7ng nh\u01b0 t\u1ea3i d\u1eef li\u1ec7u t\u1eeb m\u1ea1ng ho\u1eb7c x\u1eed l\u00fd \u1ea3nh.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">C\u00e1ch s\u1eed d\u1ee5ng <\/span><span style=\"font-weight: 400;\">DispatchQueue<\/span><span style=\"font-weight: 400;\"> \u0111\u1ec3 th\u1ef1c hi\u1ec7n c\u00f4ng vi\u1ec7c b\u1ea5t \u0111\u1ed3ng b\u1ed9:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">DispatchQueue<\/span><span style=\"font-weight: 400;\"> l\u00e0 m\u1ed9t ph\u1ea7n c\u1ee7a GCD cho ph\u00e9p b\u1ea1n x\u00e1c \u0111\u1ecbnh h\u00e0ng \u0111\u1ee3i t\u00e1c v\u1ee5 v\u00e0 ki\u1ec3m so\u00e1t khi n\u00e0o v\u00e0 \u1edf \u0111\u00e2u c\u00e1c t\u00e1c v\u1ee5 n\u00e0y s\u1ebd \u0111\u01b0\u1ee3c th\u1ef1c hi\u1ec7n.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">C\u00f3 hai lo\u1ea1i h\u00e0ng \u0111\u1ee3i ph\u1ed5 bi\u1ebfn:<\/span>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">Main Queue: Th\u1ef1c hi\u1ec7n t\u00e1c v\u1ee5 tr\u00ean lu\u1ed3ng ch\u00ednh (UI).<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">Global Queue: Th\u1ef1c hi\u1ec7n c\u00e1c t\u00e1c v\u1ee5 tr\u00ean c\u00e1c lu\u1ed3ng n\u1ec1n (background).<\/span><\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">D\u01b0\u1edbi \u0111\u00e2y l\u00e0 v\u00ed d\u1ee5 s\u1eed d\u1ee5ng <\/span><span style=\"font-weight: 400;\">DispatchQueue<\/span><span style=\"font-weight: 400;\"> \u0111\u1ec3 th\u1ef1c hi\u1ec7n c\u00f4ng vi\u1ec7c b\u1ea5t \u0111\u1ed3ng b\u1ed9:<\/span><\/p>\n<pre><span style=\"font-weight: 400;\">import Foundation<\/span>\r\n\r\n<span style=\"font-weight: 400;\">func fetchDataInBackground() {<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\/\/ S\u1eed d\u1ee5ng Global Queue \u0111\u1ec3 t\u1ea3i d\u1eef li\u1ec7u kh\u00f4ng \u0111\u1ed3ng b\u1ed9<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0DispatchQueue.global(qos: .background).async {<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\/\/ Gi\u1ea3 l\u1eadp t\u00e1c v\u1ee5 n\u1eb7ng nh\u01b0 t\u1ea3i d\u1eef li\u1ec7u<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0print(\"B\u1eaft \u0111\u1ea7u t\u1ea3i d\u1eef li\u1ec7u trong n\u1ec1n\")<\/span>\r\n\r\n<span style=\"font-weight: 400;\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\/\/ Gi\u1ea3 l\u1eadp th\u1eddi gian x\u1eed l\u00fd<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0sleep(2)\u00a0 \/\/ V\u00ed d\u1ee5, ch\u1edd 2 gi\u00e2y<\/span>\r\n\r\n<span style=\"font-weight: 400;\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0print(\"D\u1eef li\u1ec7u t\u1ea3i xong\")<\/span>\r\n\r\n<span style=\"font-weight: 400;\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\/\/ Chuy\u1ec3n sang Main Queue \u0111\u1ec3 c\u1eadp nh\u1eadt giao di\u1ec7n<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0DispatchQueue.main.async {<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0print(\"C\u1eadp nh\u1eadt giao di\u1ec7n ng\u01b0\u1eddi d\u00f9ng tr\u00ean lu\u1ed3ng ch\u00ednh\")<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0}<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0}<\/span>\r\n<span style=\"font-weight: 400;\">}<\/span>\r\n<span style=\"font-weight: 400;\">\r\nfetchDataInBackground()<\/span><\/pre>\n<p><span style=\"font-weight: 400;\">Gi\u1ea3i th\u00edch:<\/span><\/p>\n<ol>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">DispatchQueue.global(qos:): T\u1ea1o m\u1ed9t h\u00e0ng \u0111\u1ee3i n\u1ec1n v\u1edbi m\u1ee9c \u01b0u ti\u00ean (<\/span><span style=\"font-weight: 400;\">qos<\/span><span style=\"font-weight: 400;\"> &#8211; quality of service) l\u00e0 <\/span><span style=\"font-weight: 400;\">.background<\/span><span style=\"font-weight: 400;\"> \u0111\u1ec3 th\u1ef1c hi\u1ec7n c\u00e1c t\u00e1c v\u1ee5 kh\u00f4ng \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn giao di\u1ec7n.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">async: Ch\u1ea1y t\u00e1c v\u1ee5 m\u1ed9t c\u00e1ch b\u1ea5t \u0111\u1ed3ng b\u1ed9, tr\u00e1nh l\u00e0m kh\u00f3a giao di\u1ec7n ng\u01b0\u1eddi d\u00f9ng.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">DispatchQueue.main.async: Sau khi ho\u00e0n th\u00e0nh t\u00e1c v\u1ee5 n\u1ec1n, s\u1eed d\u1ee5ng <\/span><span style=\"font-weight: 400;\">DispatchQueue.main.async<\/span><span style=\"font-weight: 400;\"> \u0111\u1ec3 chuy\u1ec3n v\u1ec1 lu\u1ed3ng ch\u00ednh, c\u1eadp nh\u1eadt giao di\u1ec7n ng\u01b0\u1eddi d\u00f9ng an to\u00e0n.<\/span><\/li>\n<\/ol>\n<p><span style=\"font-weight: 400;\">Khi n\u00e0o n\u00ean s\u1eed d\u1ee5ng GCD v\u1edbi <\/span><span style=\"font-weight: 400;\">DispatchQueue<\/span><span style=\"font-weight: 400;\">:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Khi c\u1ea7n th\u1ef1c hi\u1ec7n c\u00e1c t\u00e1c v\u1ee5 n\u1eb7ng (t\u1ea3i d\u1eef li\u1ec7u, x\u1eed l\u00fd \u1ea3nh) m\u00e0 kh\u00f4ng \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn tr\u1ea3i nghi\u1ec7m ng\u01b0\u1eddi d\u00f9ng.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Khi c\u1ea7n c\u1eadp nh\u1eadt giao di\u1ec7n ho\u1eb7c k\u1ebft qu\u1ea3 t\u00ednh to\u00e1n sau khi ho\u00e0n t\u1ea5t t\u00e1c v\u1ee5 n\u1ec1n.<\/span><\/li>\n<\/ul>\n<h3><strong>S\u1ef1 kh\u00e1c nhau gi\u1eefa Main Thread v\u00e0 Background Thread trong iOS l\u00e0 g\u00ec? T\u1ea1i sao c\u1ea7n ph\u00e2n bi\u1ec7t ch\u00fang?<\/strong><\/h3>\n<table>\n<tbody>\n<tr>\n<td><span style=\"font-weight: 400;\">Thu\u1ed9c t\u00ednh\u00a0<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Main Thread\u00a0<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Backgroud Thread<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">\u0110\u1ecbnh ngh\u0129a<\/span><\/td>\n<td><span style=\"font-weight: 400;\">L\u00e0 lu\u1ed3ng ch\u00ednh, n\u01a1i th\u1ef1c hi\u1ec7n t\u1ea5t c\u1ea3 t\u00e1c v\u1ee5 li\u00ean quan \u0111\u1ebfn giao di\u1ec7n ng\u01b0\u1eddi d\u00f9ng (UI).<\/span><\/td>\n<td><span style=\"font-weight: 400;\">L\u00e0 lu\u1ed3ng n\u1ec1n, th\u1ef1c hi\u1ec7n c\u00e1c t\u00e1c v\u1ee5 kh\u00f4ng y\u00eau c\u1ea7u c\u1eadp nh\u1eadt tr\u1ef1c ti\u1ebfp l\u00ean UI.<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">Nhi\u1ec7m v\u1ee5 ch\u00ednh<\/span><\/td>\n<td><span style=\"font-weight: 400;\">C\u1eadp nh\u1eadt giao di\u1ec7n, x\u1eed l\u00fd c\u00e1c t\u01b0\u01a1ng t\u00e1c ng\u01b0\u1eddi d\u00f9ng nh\u01b0 ch\u1ea1m, cu\u1ed9n, v\u00e0 thao t\u00e1c UI.<\/span><\/td>\n<td><span style=\"font-weight: 400;\">X\u1eed l\u00fd t\u00e1c v\u1ee5 n\u1eb7ng (t\u1ea3i d\u1eef li\u1ec7u t\u1eeb m\u1ea1ng, x\u1eed l\u00fd \u1ea3nh, t\u00ednh to\u00e1n) m\u00e0 kh\u00f4ng l\u00e0m \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn giao di\u1ec7n.<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">Y\u00eau c\u1ea7u ch\u00ednh<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Ph\u1ea3i ch\u1ea1y tr\u00ean Main Thread khi c\u1eadp nh\u1eadt UI (th\u1ef1c hi\u1ec7n c\u00e1c thao t\u00e1c v\u1edbi UIView).<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Th\u00edch h\u1ee3p cho c\u00e1c t\u00e1c v\u1ee5 c\u1ea7n nhi\u1ec1u th\u1eddi gian x\u1eed l\u00fd \u0111\u1ec3 kh\u00f4ng l\u00e0m ch\u1eadm giao di\u1ec7n.<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h3><strong>Auto Layout l\u00e0 g\u00ec? L\u00e0m th\u1ebf n\u00e0o \u0111\u1ec3 t\u1ea1o m\u1ed9t giao di\u1ec7n t\u01b0\u01a1ng th\u00edch v\u1edbi nhi\u1ec1u k\u00edch th\u01b0\u1edbc m\u00e0n h\u00ecnh?<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">Auto Layout<\/span><span style=\"font-weight: 400;\"> l\u00e0 m\u1ed9t h\u1ec7 th\u1ed1ng trong iOS \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng \u0111\u1ec3 x\u00e1c \u0111\u1ecbnh v\u1ecb tr\u00ed v\u00e0 k\u00edch th\u01b0\u1edbc c\u1ee7a c\u00e1c th\u00e0nh ph\u1ea7n giao di\u1ec7n ng\u01b0\u1eddi d\u00f9ng (UI) m\u1ed9t c\u00e1ch linh ho\u1ea1t v\u00e0 \u0111\u1ed9ng, d\u1ef1a tr\u00ean c\u00e1c r\u00e0ng bu\u1ed9c (constraints). H\u1ec7 th\u1ed1ng n\u00e0y gi\u00fap t\u1ef1 \u0111\u1ed9ng \u0111i\u1ec1u ch\u1ec9nh b\u1ed1 c\u1ee5c c\u1ee7a \u1ee9ng d\u1ee5ng cho ph\u00f9 h\u1ee3p v\u1edbi c\u00e1c k\u00edch th\u01b0\u1edbc m\u00e0n h\u00ecnh kh\u00e1c nhau, h\u01b0\u1edbng m\u00e0n h\u00ecnh (portrait ho\u1eb7c landscape), v\u00e0 c\u00e1c thi\u1ebft b\u1ecb kh\u00e1c nhau (iPhone, iPad).<\/span><\/p>\n<p><span style=\"font-weight: 400;\">C\u00e1ch t\u1ea1o giao di\u1ec7n t\u01b0\u01a1ng th\u00edch v\u1edbi nhi\u1ec1u k\u00edch th\u01b0\u1edbc m\u00e0n h\u00ecnh b\u1eb1ng Auto Layout:<\/span><\/p>\n<ol>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">S\u1eed d\u1ee5ng Constraints:<\/span>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">Thi\u1ebft l\u1eadp c\u00e1c r\u00e0ng bu\u1ed9c gi\u1eefa c\u00e1c th\u00e0nh ph\u1ea7n UI \u0111\u1ec3 x\u00e1c \u0111\u1ecbnh c\u00e1ch m\u00e0 ch\u00fang s\u1ebd di chuy\u1ec3n ho\u1eb7c thay \u0111\u1ed5i k\u00edch th\u01b0\u1edbc khi k\u00edch th\u01b0\u1edbc m\u00e0n h\u00ecnh thay \u0111\u1ed5i.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">V\u00ed d\u1ee5: b\u1ea1n c\u00f3 th\u1ec3 \u0111\u1eb7t m\u1ed9t n\u00fat c\u00e1ch c\u1ea1nh tr\u00ean 20 \u0111i\u1ec3m v\u00e0 c\u00e1ch c\u1ea1nh tr\u00e1i 15 \u0111i\u1ec3m. \u0110i\u1ec1u n\u00e0y \u0111\u1ea3m b\u1ea3o r\u1eb1ng n\u00fat s\u1ebd gi\u1eef kho\u1ea3ng c\u00e1ch nh\u1ea5t \u0111\u1ecbnh v\u1edbi c\u00e1c c\u1ea1nh c\u1ee7a m\u00e0n h\u00ecnh.<\/span><\/li>\n<\/ul>\n<\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">H\u1ec7 th\u1ed1ng Size Classes:<\/span>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">S\u1eed d\u1ee5ng Size Classes \u0111\u1ec3 x\u00e1c \u0111\u1ecbnh c\u00e1ch b\u1ed1 tr\u00ed cho c\u00e1c thi\u1ebft b\u1ecb v\u00e0 h\u01b0\u1edbng m\u00e0n h\u00ecnh kh\u00e1c nhau.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">B\u1ea1n c\u00f3 th\u1ec3 thi\u1ebft l\u1eadp c\u00e1c giao di\u1ec7n kh\u00e1c nhau cho c\u00e1c size class kh\u00e1c nhau, v\u00ed d\u1ee5 nh\u01b0 <\/span><i><span style=\"font-weight: 400;\">compact width<\/span><\/i><span style=\"font-weight: 400;\"> cho iPhone v\u00e0 <\/span><i><span style=\"font-weight: 400;\">regular width<\/span><\/i><span style=\"font-weight: 400;\"> cho iPad.<\/span><\/li>\n<\/ul>\n<\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">B\u1ed1 c\u1ee5c t\u01b0\u01a1ng th\u00edch (Adaptive Layout):<\/span>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">T\u1ea1o c\u00e1c b\u1ed1 c\u1ee5c linh ho\u1ea1t s\u1eed d\u1ee5ng c\u00e1c View v\u00e0 Stack Views.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">Stack Views gi\u00fap b\u1ea1n d\u1ec5 d\u00e0ng s\u1eafp x\u1ebfp c\u00e1c th\u00e0nh ph\u1ea7n UI theo chi\u1ec1u ngang ho\u1eb7c chi\u1ec1u d\u1ecdc m\u00e0 kh\u00f4ng c\u1ea7n thi\u1ebft l\u1eadp nhi\u1ec1u r\u00e0ng bu\u1ed9c.<\/span><\/li>\n<\/ul>\n<\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Ch\u1ea1y th\u1eed tr\u00ean nhi\u1ec1u thi\u1ebft b\u1ecb:<\/span><\/li>\n<\/ol>\n<p><span style=\"font-weight: 400;\">S\u1eed d\u1ee5ng Simulator ho\u1eb7c c\u00e1c thi\u1ebft b\u1ecb th\u1eadt \u0111\u1ec3 ki\u1ec3m tra giao di\u1ec7n tr\u00ean nhi\u1ec1u k\u00edch th\u01b0\u1edbc m\u00e0n h\u00ecnh kh\u00e1c nhau, \u0111\u1ea3m b\u1ea3o r\u1eb1ng giao di\u1ec7n hi\u1ec3n th\u1ecb \u0111\u1eb9p m\u1eaft v\u00e0 d\u1ec5 s\u1eed d\u1ee5ng tr\u00ean m\u1ecdi thi\u1ebft b\u1ecb.<\/span><\/p>\n<h2><span class=\"ez-toc-section\" id=\"Cac_cau_hoi_phong_van_iOS_Developer_lien_quan_den_UIUX_Kien_truc\"><\/span><strong>C\u00e1c c\u00e2u h\u1ecfi ph\u1ecfng v\u1ea5n iOS Developer li\u00ean quan \u0111\u1ebfn UI\/UX &amp; Ki\u1ebfn tr\u00fac<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n<h3><strong>Gi\u1ea3i th\u00edch MVVM l\u00e0 g\u00ec? N\u00f3 kh\u00e1c g\u00ec so v\u1edbi MVC trong iOS?<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">MVVM (Model-View-ViewModel):<\/span><\/p>\n<p><span style=\"font-weight: 400;\">MVVM<\/span><span style=\"font-weight: 400;\"> l\u00e0 m\u1ed9t m\u1eabu ki\u1ebfn tr\u00fac ph\u1ea7n m\u1ec1m \u0111\u01b0\u1ee3c thi\u1ebft k\u1ebf \u0111\u1ec3 h\u1ed7 tr\u1ee3 ph\u00e1t tri\u1ec3n \u1ee9ng d\u1ee5ng v\u1edbi giao di\u1ec7n ng\u01b0\u1eddi d\u00f9ng phong ph\u00fa. N\u00f3 gi\u00fap t\u00e1ch bi\u1ec7t logic \u0111i\u1ec1u khi\u1ec3n (business logic) kh\u1ecfi giao di\u1ec7n ng\u01b0\u1eddi d\u00f9ng, t\u1ea1o \u0111i\u1ec1u ki\u1ec7n cho vi\u1ec7c ph\u00e1t tri\u1ec3n v\u00e0 b\u1ea3o tr\u00ec d\u1ec5 d\u00e0ng h\u01a1n.<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Model: \u0110\u1ea1i di\u1ec7n cho d\u1eef li\u1ec7u v\u00e0 c\u00e1c quy t\u1eafc kinh doanh. Model kh\u00f4ng bi\u1ebft g\u00ec v\u1ec1 View ho\u1eb7c ViewModel.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">View: L\u00e0 giao di\u1ec7n ng\u01b0\u1eddi d\u00f9ng (UI) m\u00e0 ng\u01b0\u1eddi d\u00f9ng t\u01b0\u01a1ng t\u00e1c. View ch\u1ec9 nh\u1eadn th\u00f4ng tin t\u1eeb ViewModel v\u00e0 kh\u00f4ng x\u1eed l\u00fd logic kinh doanh.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">ViewModel: L\u00e0 c\u1ea7u n\u1ed1i gi\u1eefa Model v\u00e0 View. N\u00f3 ch\u1ee9a logic \u0111i\u1ec1u khi\u1ec3n v\u00e0 c\u00e1c thu\u1ed9c t\u00ednh c\u1ea7n thi\u1ebft \u0111\u1ec3 hi\u1ec3n th\u1ecb tr\u00ean View. ViewModel c\u00f3 th\u1ec3 c\u00f3 c\u00e1c thu\u1ed9c t\u00ednh th\u00f4ng b\u00e1o cho View v\u1ec1 nh\u1eefng thay \u0111\u1ed5i c\u1ea7n \u0111\u01b0\u1ee3c c\u1eadp nh\u1eadt.<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">MVC (Model-View-Controller):<\/span><\/p>\n<p><span style=\"font-weight: 400;\">MVC<\/span><span style=\"font-weight: 400;\"> l\u00e0 m\u1ed9t m\u1eabu ki\u1ebfn tr\u00fac ph\u1ed5 bi\u1ebfn trong ph\u00e1t tri\u1ec3n \u1ee9ng d\u1ee5ng, bao g\u1ed3m ba th\u00e0nh ph\u1ea7n ch\u00ednh:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Model: T\u01b0\u01a1ng t\u1ef1 nh\u01b0 trong MVVM, Model ch\u1ee9a d\u1eef li\u1ec7u v\u00e0 logic kinh doanh.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">View: Giao di\u1ec7n ng\u01b0\u1eddi d\u00f9ng m\u00e0 ng\u01b0\u1eddi d\u00f9ng t\u01b0\u01a1ng t\u00e1c.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Controller: L\u00e0 c\u1ea7u n\u1ed1i gi\u1eefa Model v\u00e0 View. Controller nh\u1eadn c\u00e1c s\u1ef1 ki\u1ec7n t\u1eeb View, c\u1eadp nh\u1eadt Model v\u00e0 sau \u0111\u00f3 c\u1eadp nh\u1eadt View.<\/span><\/li>\n<\/ul>\n<h3><strong>Combine trong iOS l\u00e0 g\u00ec? Khi n\u00e0o n\u00ean s\u1eed d\u1ee5ng?<\/strong><\/h3>\n<p><a href=\"https:\/\/developer.apple.com\/documentation\/combine\" target=\"_blank\" rel=\"noopener\"><span style=\"font-weight: 400;\">Combine<\/span><\/a><span style=\"font-weight: 400;\"> l\u00e0 m\u1ed9t framework \u0111\u01b0\u1ee3c Apple gi\u1edbi thi\u1ec7u trong iOS 13, cho ph\u00e9p b\u1ea1n x\u00e2y d\u1ef1ng c\u00e1c \u1ee9ng d\u1ee5ng s\u1eed d\u1ee5ng l\u1eadp tr\u00ecnh ph\u1ea3n \u1ee9ng. N\u00f3 cung c\u1ea5p c\u00e1c c\u00f4ng c\u1ee5 \u0111\u1ec3 x\u1eed l\u00fd c\u00e1c s\u1ef1 ki\u1ec7n b\u1ea5t \u0111\u1ed3ng b\u1ed9 v\u00e0 qu\u1ea3n l\u00fd d\u1eef li\u1ec7u theo c\u00e1ch \u0111\u01a1n gi\u1ea3n v\u00e0 d\u1ec5 hi\u1ec3u.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">T\u00ednh n\u0103ng ch\u00ednh c\u1ee7a Combine:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Publishers and Subscribers: Combine ho\u1ea1t \u0111\u1ed9ng d\u1ef1a tr\u00ean m\u00f4 h\u00ecnh nh\u00e0 xu\u1ea5t b\u1ea3n (publisher) v\u00e0 ng\u01b0\u1eddi \u0111\u0103ng k\u00fd (subscriber). Publishers ph\u00e1t h\u00e0nh c\u00e1c gi\u00e1 tr\u1ecb theo th\u1eddi gian v\u00e0 Subscribers nh\u1eadn c\u00e1c gi\u00e1 tr\u1ecb \u0111\u00f3.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Operators: Combine cung c\u1ea5p m\u1ed9t lo\u1ea1t c\u00e1c to\u00e1n t\u1eed (operators) \u0111\u1ec3 bi\u1ebfn \u0111\u1ed5i v\u00e0 k\u1ebft h\u1ee3p c\u00e1c gi\u00e1 tr\u1ecb, cho ph\u00e9p b\u1ea1n th\u1ef1c hi\u1ec7n c\u00e1c thao t\u00e1c ph\u1ee9c t\u1ea1p tr\u00ean d\u1eef li\u1ec7u m\u1ed9t c\u00e1ch d\u1ec5 d\u00e0ng.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Chaining: B\u1ea1n c\u00f3 th\u1ec3 k\u1ebft h\u1ee3p nhi\u1ec1u to\u00e1n t\u1eed \u0111\u1ec3 t\u1ea1o ra m\u1ed9t chu\u1ed7i x\u1eed l\u00fd d\u1eef li\u1ec7u, gi\u00fap t\u0103ng t\u00ednh d\u1ec5 \u0111\u1ecdc v\u00e0 b\u1ea3o tr\u00ec c\u1ee7a m\u00e3.<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">Khi n\u00e0o n\u00ean s\u1eed d\u1ee5ng Combine:<\/span><\/p>\n<ol>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">X\u1eed l\u00fd d\u1eef li\u1ec7u b\u1ea5t \u0111\u1ed3ng b\u1ed9: Khi b\u1ea1n c\u1ea7n theo d\u00f5i v\u00e0 ph\u1ea3n \u1ee9ng v\u1edbi c\u00e1c thay \u0111\u1ed5i trong d\u1eef li\u1ec7u, ch\u1eb3ng h\u1ea1n nh\u01b0 t\u1eeb m\u1ea1ng, c\u01a1 s\u1edf d\u1eef li\u1ec7u ho\u1eb7c giao di\u1ec7n ng\u01b0\u1eddi d\u00f9ng.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">T\u01b0\u01a1ng t\u00e1c v\u1edbi UI: Khi b\u1ea1n mu\u1ed1n c\u1eadp nh\u1eadt giao di\u1ec7n ng\u01b0\u1eddi d\u00f9ng d\u1ef1a tr\u00ean c\u00e1c s\u1ef1 ki\u1ec7n kh\u00e1c nhau, nh\u01b0 nh\u1ea5n n\u00fat, nh\u1eadp d\u1eef li\u1ec7u, ho\u1eb7c thay \u0111\u1ed5i trong m\u00f4 h\u00ecnh.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">X\u1eed l\u00fd chu\u1ed7i d\u1eef li\u1ec7u ph\u1ee9c t\u1ea1p: Khi b\u1ea1n c\u1ea7n th\u1ef1c hi\u1ec7n c\u00e1c thao t\u00e1c nh\u01b0 l\u1ecdc, \u00e1nh x\u1ea1, v\u00e0 k\u1ebft h\u1ee3p nhi\u1ec1u ngu\u1ed3n d\u1eef li\u1ec7u m\u00e0 kh\u00f4ng l\u00e0m r\u1ed1i m\u00e3.<\/span><\/li>\n<\/ol>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-81602\" src=\"https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/11\/cau-hoi-phong-van-ios-developer-4-vippro.jpg\" alt=\"c\u00e2u h\u1ecfi ph\u1ecfng v\u1ea5n ios developer - itviec blog\" width=\"1200\" height=\"674\" srcset=\"https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/11\/cau-hoi-phong-van-ios-developer-4-vippro.jpg 1200w, https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/11\/cau-hoi-phong-van-ios-developer-4-vippro-300x169.jpg 300w, https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/11\/cau-hoi-phong-van-ios-developer-4-vippro-700x393.jpg 640w, https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/11\/cau-hoi-phong-van-ios-developer-4-vippro-200x112.jpg 200w, https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/11\/cau-hoi-phong-van-ios-developer-4-vippro-100x56.jpg 100w\" sizes=\"auto, (max-width: 1200px) 100vw, 1200px\" \/><\/p>\n<h3><strong>T\u1ea1i sao SwiftUI d\u00f9ng Struct cho View ch\u1ee9 kh\u00f4ng ph\u1ea3i Class?<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">SwiftUI s\u1eed d\u1ee5ng <\/span><span style=\"font-weight: 400;\">Struct<\/span><span style=\"font-weight: 400;\"> cho c\u00e1c View v\u00ec m\u1ed9t s\u1ed1 l\u00fd do ch\u00ednh:<\/span><\/p>\n<ol>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Hi\u1ec7u su\u1ea5t v\u00e0 T\u1ed1i \u01b0u h\u00f3a B\u1ed9 nh\u1edb: <\/span><i><span style=\"font-weight: 400;\">Struct<\/span><\/i><span style=\"font-weight: 400;\"> l\u00e0 m\u1ed9t ki\u1ec3u d\u1eef li\u1ec7u <\/span><i><span style=\"font-weight: 400;\">value type<\/span><\/i><span style=\"font-weight: 400;\">, ngh\u0129a l\u00e0 m\u1ed7i khi m\u1ed9t <\/span><i><span style=\"font-weight: 400;\">Struct<\/span><\/i><span style=\"font-weight: 400;\"> \u0111\u01b0\u1ee3c t\u1ea1o m\u1edbi ho\u1eb7c thay \u0111\u1ed5i, n\u00f3 s\u1ebd t\u1ea1o m\u1ed9t b\u1ea3n sao \u0111\u1ed9c l\u1eadp. \u0110i\u1ec1u n\u00e0y gi\u00fap SwiftUI d\u1ec5 d\u00e0ng t\u1ea1o ra c\u00e1c View m\u1edbi khi d\u1eef li\u1ec7u thay \u0111\u1ed5i, gi\u1ea3m thi\u1ec3u t\u00e1c \u0111\u1ed9ng \u0111\u1ebfn b\u1ed9 nh\u1edb so v\u1edbi <\/span><i><span style=\"font-weight: 400;\">Class<\/span><\/i><span style=\"font-weight: 400;\">, v\u1ed1n l\u00e0 <\/span><i><span style=\"font-weight: 400;\">reference type<\/span><\/i><span style=\"font-weight: 400;\"> v\u00e0 th\u01b0\u1eddng ph\u1ee9c t\u1ea1p h\u01a1n khi c\u1ea7n qu\u1ea3n l\u00fd v\u00f2ng \u0111\u1eddi.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Immutable v\u00e0 Predictable: Trong SwiftUI, <\/span><i><span style=\"font-weight: 400;\">Struct<\/span><\/i><span style=\"font-weight: 400;\"> gi\u00fap gi\u1eef c\u00e1c View b\u1ea5t bi\u1ebfn (immutable), ngh\u0129a l\u00e0 tr\u1ea1ng th\u00e1i c\u1ee7a m\u1ed9t View s\u1ebd kh\u00f4ng thay \u0111\u1ed5i sau khi \u0111\u01b0\u1ee3c kh\u1edfi t\u1ea1o. \u0110i\u1ec1u n\u00e0y gi\u00fap \u0111\u1ea3m b\u1ea3o r\u1eb1ng View s\u1ebd kh\u00f4ng g\u00e2y ra c\u00e1c tr\u1ea1ng th\u00e1i kh\u00f3 l\u01b0\u1eddng v\u00e0 d\u1ec5 d\u00e0ng t\u1ed1i \u01b0u h\u00f3a. SwiftUI c\u00f3 th\u1ec3 d\u1ef1 \u0111o\u00e1n ch\u00ednh x\u00e1c c\u00e1c thay \u0111\u1ed5i trong giao di\u1ec7n d\u1ef1a tr\u00ean d\u1eef li\u1ec7u v\u00e0 tr\u1ea1ng th\u00e1i c\u1ee7a <\/span><i><span style=\"font-weight: 400;\">Struct<\/span><\/i><span style=\"font-weight: 400;\">, t\u1eeb \u0111\u00f3 gi\u1ea3m thi\u1ec3u c\u00e1c l\u1ed7i kh\u00f4ng mong mu\u1ed1n.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">D\u1ec5 Qu\u1ea3n l\u00fd v\u00e0 Update: V\u1edbi <\/span><i><span style=\"font-weight: 400;\">Struct<\/span><\/i><span style=\"font-weight: 400;\">, SwiftUI c\u00f3 th\u1ec3 so s\u00e1nh nhanh ch\u00f3ng gi\u1eefa c\u00e1c phi\u00ean b\u1ea3n c\u1ee7a View khi c\u1ea7n c\u1eadp nh\u1eadt giao di\u1ec7n. N\u1ebfu c\u00f3 s\u1ef1 thay \u0111\u1ed5i, SwiftUI ch\u1ec9 c\u1ea7n c\u1eadp nh\u1eadt ph\u1ea7n b\u1ecb \u1ea3nh h\u01b0\u1edfng thay v\u00ec ph\u1ea3i c\u1eadp nh\u1eadt to\u00e0n b\u1ed9. \u0110i\u1ec1u n\u00e0y gi\u00fap giao di\u1ec7n m\u01b0\u1ee3t m\u00e0 v\u00e0 t\u0103ng hi\u1ec7u su\u1ea5t \u0111\u00e1ng k\u1ec3.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Concurrency: <\/span><i><span style=\"font-weight: 400;\">Struct<\/span><\/i><span style=\"font-weight: 400;\"> \u0111\u01b0\u1ee3c qu\u1ea3n l\u00fd d\u1ec5 d\u00e0ng trong l\u1eadp tr\u00ecnh \u0111a lu\u1ed3ng. V\u1edbi <\/span><i><span style=\"font-weight: 400;\">Struct<\/span><\/i><span style=\"font-weight: 400;\">, SwiftUI c\u00f3 th\u1ec3 sao ch\u00e9p d\u1eef li\u1ec7u c\u1ee7a View m\u00e0 kh\u00f4ng s\u1ee3 g\u1eb7p ph\u1ea3i v\u1ea5n \u0111\u1ec1 khi truy c\u1eadp b\u1ed9 nh\u1edb gi\u1eefa c\u00e1c lu\u1ed3ng, gi\u00fap x\u1eed l\u00fd \u0111\u1ed3ng th\u1eddi (concurrency) an to\u00e0n v\u00e0 hi\u1ec7u qu\u1ea3 h\u01a1n.<\/span><\/li>\n<\/ol>\n<h3><strong>L\u00e0m th\u1ebf n\u00e0o \u0111\u1ec3 s\u1eed d\u1ee5ng Animation trong SwiftUI? Cho m\u1ed9t v\u00ed d\u1ee5<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">SwiftUI cung c\u1ea5p m\u1ed9t API \u0111\u01a1n gi\u1ea3n \u0111\u1ec3 th\u00eam hi\u1ec7u \u1ee9ng chuy\u1ec3n \u0111\u1ed9ng v\u00e0o c\u00e1c View. B\u1ea1n c\u00f3 th\u1ec3 s\u1eed d\u1ee5ng modifier <\/span><span style=\"font-weight: 400;\">.animation()<\/span><span style=\"font-weight: 400;\"> \u0111\u1ec3 \u00e1p d\u1ee5ng hi\u1ec7u \u1ee9ng khi c\u00f3 s\u1ef1 thay \u0111\u1ed5i tr\u1ea1ng th\u00e1i, ho\u1eb7c s\u1eed d\u1ee5ng c\u00e1c ph\u01b0\u01a1ng th\u1ee9c <\/span><span style=\"font-weight: 400;\">.withAnimation()<\/span><span style=\"font-weight: 400;\"> \u0111\u1ec3 th\u1ef1c hi\u1ec7n chuy\u1ec3n \u0111\u1ed9ng trong qu\u00e1 tr\u00ecnh thay \u0111\u1ed5i tr\u1ea1ng th\u00e1i.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">V\u00ed d\u1ee5 c\u01a1 b\u1ea3n v\u1ec1 Animation trong SwiftUI<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Trong v\u00ed d\u1ee5 n\u00e0y, khi nh\u1ea5n v\u00e0o n\u00fat, h\u00ecnh tr\u00f2n s\u1ebd thay \u0111\u1ed5i k\u00edch th\u01b0\u1edbc m\u1ed9t c\u00e1ch m\u01b0\u1ee3t m\u00e0 b\u1eb1ng c\u00e1ch s\u1eed d\u1ee5ng <\/span><span style=\"font-weight: 400;\">withAnimation<\/span><span style=\"font-weight: 400;\">.<\/span><\/p>\n<pre><span style=\"font-weight: 400;\">import SwiftUI<\/span>\r\n\r\n<span style=\"font-weight: 400;\">struct ContentView: View {<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0@State private var isExpanded = false<\/span>\r\n\r\n<span style=\"font-weight: 400;\">\u00a0\u00a0\u00a0\u00a0var body: some View {<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0VStack {<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Circle()<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0.frame(width: isExpanded ? 200 : 100, height: isExpanded ? 200 : 100)<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0.foregroundColor(.blue)<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0.animation(.easeInOut(duration: 0.5)) \/\/ Th\u00eam animation v\u00e0o tr\u1ea1ng th\u00e1i<\/span>\r\n\r\n<span style=\"font-weight: 400;\">\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Button(\"Animate Circle\") {<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0withAnimation {<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0isExpanded.toggle() \/\/ Thay \u0111\u1ed5i tr\u1ea1ng th\u00e1i \u0111\u1ec3 k\u00edch ho\u1ea1t animation<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0}<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0}<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0.padding()<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0}<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0}<\/span>\r\n<span style=\"font-weight: 400;\">}<\/span><\/pre>\n<p><span style=\"font-weight: 400;\">Gi\u1ea3i th\u00edch<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">@State: Bi\u1ebfn <\/span><span style=\"font-weight: 400;\">isExpanded<\/span><span style=\"font-weight: 400;\"> l\u00e0 m\u1ed9t bi\u1ebfn tr\u1ea1ng th\u00e1i d\u00f9ng \u0111\u1ec3 ki\u1ec3m so\u00e1t k\u00edch th\u01b0\u1edbc c\u1ee7a h\u00ecnh tr\u00f2n.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">withAnimation: Khi nh\u1ea5n v\u00e0o n\u00fat, <\/span><span style=\"font-weight: 400;\">isExpanded<\/span><span style=\"font-weight: 400;\"> thay \u0111\u1ed5i, v\u00e0 nh\u1edd <\/span><span style=\"font-weight: 400;\">withAnimation<\/span><span style=\"font-weight: 400;\">, SwiftUI t\u1ef1 \u0111\u1ed9ng c\u1eadp nh\u1eadt View v\u1edbi hi\u1ec7u \u1ee9ng chuy\u1ec3n \u0111\u1ed9ng.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">.animation(.easeInOut(duration: 0.5)): T\u1ea1o animation v\u1edbi ki\u1ec3u <\/span><i><span style=\"font-weight: 400;\">easeInOut<\/span><\/i><span style=\"font-weight: 400;\"> v\u00e0 th\u1eddi gian k\u00e9o d\u00e0i 0.5 gi\u00e2y, gi\u00fap h\u00ecnh tr\u00f2n thay \u0111\u1ed5i k\u00edch th\u01b0\u1edbc m\u01b0\u1ee3t m\u00e0.<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">C\u00e1c ki\u1ec3u Animation ph\u1ed5 bi\u1ebfn trong SwiftUI<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">.linear<\/span><span style=\"font-weight: 400;\">: T\u1ed1c \u0111\u1ed9 animation kh\u00f4ng \u0111\u1ed5i.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">.easeIn<\/span><span style=\"font-weight: 400;\">: Animation b\u1eaft \u0111\u1ea7u ch\u1eadm r\u1ed3i t\u0103ng t\u1ed1c.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">.easeOut<\/span><span style=\"font-weight: 400;\">: Animation b\u1eaft \u0111\u1ea7u nhanh v\u00e0 k\u1ebft th\u00fac ch\u1eadm.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">.easeInOut<\/span><span style=\"font-weight: 400;\">: Animation k\u1ebft h\u1ee3p c\u1ea3 <\/span><i><span style=\"font-weight: 400;\">easeIn<\/span><\/i><span style=\"font-weight: 400;\"> v\u00e0 <\/span><i><span style=\"font-weight: 400;\">easeOut<\/span><\/i><span style=\"font-weight: 400;\">.<\/span><\/li>\n<\/ul>\n<h3><strong>Coordinator pattern l\u00e0 g\u00ec v\u00e0 t\u1ea1i sao n\u00f3 \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng trong iOS?<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">Coordinator pattern<\/span><span style=\"font-weight: 400;\"> l\u00e0 m\u1ed9t m\u1eabu thi\u1ebft k\u1ebf gi\u00fap t\u00e1ch bi\u1ec7t vi\u1ec7c \u0111i\u1ec1u h\u01b0\u1edbng (navigation) v\u00e0 qu\u1ea3n l\u00fd lu\u1ed3ng giao di\u1ec7n ng\u01b0\u1eddi d\u00f9ng (UI flow) kh\u1ecfi c\u00e1c <\/span><span style=\"font-weight: 400;\">UIViewController<\/span><span style=\"font-weight: 400;\">. \u0110i\u1ec1u n\u00e0y gi\u00fap l\u00e0m cho m\u00e3 ngu\u1ed3n d\u1ec5 b\u1ea3o tr\u00ec h\u01a1n v\u00e0 gi\u1ea3m b\u1edbt \u0111\u1ed9 ph\u1ee9c t\u1ea1p trong c\u00e1c <\/span><span style=\"font-weight: 400;\">ViewController<\/span><span style=\"font-weight: 400;\">, v\u00ec c\u00e1c <\/span><span style=\"font-weight: 400;\">ViewController<\/span><span style=\"font-weight: 400;\"> kh\u00f4ng c\u00f2n ph\u1ea3i ch\u1ecbu tr\u00e1ch nhi\u1ec7m v\u1ec1 vi\u1ec7c \u0111i\u1ec1u h\u01b0\u1edbng ho\u1eb7c lu\u1ed3ng logic.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">L\u1ee3i \u00edch c\u1ee7a Coordinator Pattern:<\/span><\/p>\n<ol>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Ph\u00e2n t\u00e1ch tr\u00e1ch nhi\u1ec7m: Coordinator pattern di chuy\u1ec3n logic \u0111i\u1ec1u h\u01b0\u1edbng ra kh\u1ecfi <\/span><span style=\"font-weight: 400;\">UIViewController<\/span><span style=\"font-weight: 400;\"> v\u00e0 \u0111\u1eb7t ch\u00fang v\u00e0o c\u00e1c l\u1edbp ri\u00eang g\u1ecdi l\u00e0 <\/span><i><span style=\"font-weight: 400;\">Coordinator<\/span><\/i><span style=\"font-weight: 400;\">. \u0110i\u1ec1u n\u00e0y gi\u00fap cho m\u1ed7i <\/span><span style=\"font-weight: 400;\">UIViewController<\/span><span style=\"font-weight: 400;\"> ch\u1ec9 t\u1eadp trung v\u00e0o logic ri\u00eang c\u1ee7a n\u00f3 thay v\u00ec qu\u1ea3n l\u00fd to\u00e0n b\u1ed9 lu\u1ed3ng giao di\u1ec7n.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">T\u00e1i s\u1eed d\u1ee5ng m\u00e3 d\u1ec5 d\u00e0ng: Vi\u1ec7c \u0111i\u1ec1u h\u01b0\u1edbng gi\u1eefa c\u00e1c m\u00e0n h\u00ecnh \u0111\u01b0\u1ee3c x\u1eed l\u00fd trong c\u00e1c l\u1edbp <\/span><span style=\"font-weight: 400;\">Coordinator<\/span><span style=\"font-weight: 400;\">, gi\u00fap ch\u00fang ta t\u00e1i s\u1eed d\u1ee5ng ho\u1eb7c chia s\u1ebb lu\u1ed3ng \u0111i\u1ec1u h\u01b0\u1edbng gi\u1eefa c\u00e1c ph\u1ea7n kh\u00e1c nhau c\u1ee7a \u1ee9ng d\u1ee5ng.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">T\u0103ng kh\u1ea3 n\u0103ng b\u1ea3o tr\u00ec: V\u00ec lu\u1ed3ng \u0111i\u1ec1u h\u01b0\u1edbng kh\u00f4ng n\u1eb1m trong <\/span><span style=\"font-weight: 400;\">UIViewController<\/span><span style=\"font-weight: 400;\">, m\u00e3 ngu\u1ed3n tr\u1edf n\u00ean d\u1ec5 b\u1ea3o tr\u00ec h\u01a1n. C\u00e1c thay \u0111\u1ed5i v\u1ec1 \u0111i\u1ec1u h\u01b0\u1edbng c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c th\u1ef1c hi\u1ec7n trong l\u1edbp <\/span><span style=\"font-weight: 400;\">Coordinator<\/span><span style=\"font-weight: 400;\"> m\u00e0 kh\u00f4ng \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn c\u00e1c <\/span><span style=\"font-weight: 400;\">ViewController<\/span><span style=\"font-weight: 400;\">.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Th\u00fac \u0111\u1ea9y t\u00ednh m\u00f4-\u0111un: <\/span><span style=\"font-weight: 400;\">Coordinator pattern<\/span><span style=\"font-weight: 400;\"> gi\u00fap d\u1ec5 d\u00e0ng m\u1edf r\u1ed9ng v\u00e0 th\u00eam t\u00ednh n\u0103ng m\u1edbi m\u00e0 kh\u00f4ng l\u00e0m ph\u1ee9c t\u1ea1p th\u00eam c\u00e1c l\u1edbp hi\u1ec7n c\u00f3.<\/span><\/li>\n<\/ol>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-81601\" src=\"https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/11\/cau-hoi-phong-van-ios-developer-3-vippro.png\" alt=\"c\u00e2u h\u1ecfi ph\u1ecfng v\u1ea5n ios developer - itviec blog\" width=\"1024\" height=\"501\" srcset=\"https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/11\/cau-hoi-phong-van-ios-developer-3-vippro.png 1024w, https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/11\/cau-hoi-phong-van-ios-developer-3-vippro-300x147.png 300w, https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/11\/cau-hoi-phong-van-ios-developer-3-vippro-700x342.png 640w, https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/11\/cau-hoi-phong-van-ios-developer-3-vippro-200x98.png 200w, https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/11\/cau-hoi-phong-van-ios-developer-3-vippro-100x49.png 100w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/p>\n<h3><strong>Gi\u1ea3i th\u00edch c\u00e1ch l\u00e0m vi\u1ec7c v\u1edbi UITableView v\u00e0 UICollectionView. Khi n\u00e0o n\u00ean s\u1eed d\u1ee5ng m\u1ed7i lo\u1ea1i?<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">UITableView<\/span><span style=\"font-weight: 400;\"> v\u00e0 <\/span><span style=\"font-weight: 400;\">UICollectionView<\/span><span style=\"font-weight: 400;\"> l\u00e0 hai th\u00e0nh ph\u1ea7n giao di\u1ec7n ch\u00ednh trong iOS \u0111\u1ec3 hi\u1ec3n th\u1ecb d\u1eef li\u1ec7u d\u1ea1ng danh s\u00e1ch. Ch\u00fang \u0111\u1ec1u gi\u00fap hi\u1ec3n th\u1ecb m\u1ed9t t\u1eadp h\u1ee3p c\u00e1c ph\u1ea7n t\u1eed, nh\u01b0ng m\u1ed7i lo\u1ea1i c\u00f3 \u01b0u \u0111i\u1ec3m ri\u00eang v\u00e0 ph\u00f9 h\u1ee3p cho c\u00e1c t\u00ecnh hu\u1ed1ng kh\u00e1c nhau.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">B\u1ea3ng d\u01b0\u1edbi \u0111\u00e2y s\u1ebd ph\u00e2n bi\u1ec7t nh\u1eefng \u0111i\u1ec3m kh\u00e1c nhau v\u00e0 khi n\u00e0o n\u00ean d\u00f9ng ch\u00fang cho t\u1eebng y\u00eau c\u1ea7u kh\u00e1c nhau<\/span><\/p>\n<table>\n<tbody>\n<tr>\n<td><strong>Thu\u1ed9c t\u00ednh\u00a0<\/strong><\/td>\n<td><strong>UITableView<\/strong><\/td>\n<td><strong>UICollectionView<\/strong><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">B\u1ed1 c\u1ee5c<\/span><\/td>\n<td><span style=\"font-weight: 400;\">M\u1ed9t c\u1ed9t v\u00e0 cu\u1ed9n theo chi\u1ec1u d\u1ecdc<\/span><\/td>\n<td><span style=\"font-weight: 400;\">C\u00f3 th\u1ec3 t\u00f9y ch\u1ec9nh theo d\u1ea1ng l\u01b0\u1edbi, chi\u1ec1u d\u1ecdc ho\u1eb7c ngang<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">DataSource\/Delegate<\/span><\/td>\n<td><span style=\"font-weight: 400;\">UITableViewDataSource, UITableViewDelegate<\/span><\/td>\n<td><span style=\"font-weight: 400;\">UICollectionViewDataSource, UICollectionViewDelegate<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">T\u00f9y ch\u1ec9nh layout<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Ch\u1ec9 h\u1ed7 tr\u1ee3 chi\u1ec1u d\u1ecdc<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Linh ho\u1ea1t v\u1edbi UICollectionViewLayout<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">Khi n\u00e0o n\u00ean d\u00f9ng<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Danh s\u00e1ch tuy\u1ebfn t\u00ednh, c\u1ed9t \u0111\u01a1n<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Giao di\u1ec7n d\u1ea1ng l\u01b0\u1edbi ho\u1eb7c y\u00eau c\u1ea7u b\u1ed1 c\u1ee5c ph\u1ee9c t\u1ea1p<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h3><strong>Custom View l\u00e0 g\u00ec trong iOS? Khi n\u00e0o n\u00ean t\u1ea1o m\u1ed9t custom view?<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">Custom View l\u00e0 m\u1ed9t th\u00e0nh ph\u1ea7n giao di\u1ec7n t\u1ef1 \u0111\u1ecbnh ngh\u0129a trong iOS, \u0111\u01b0\u1ee3c x\u00e2y d\u1ef1ng t\u1eeb c\u00e1c l\u1edbp con c\u1ee7a <\/span><span style=\"font-weight: 400;\">UIView<\/span><span style=\"font-weight: 400;\"> \u0111\u1ec3 t\u1ea1o m\u1ed9t giao di\u1ec7n ng\u01b0\u1eddi d\u00f9ng \u0111\u1ed9c \u0111\u00e1o, ph\u00f9 h\u1ee3p v\u1edbi y\u00eau c\u1ea7u c\u1ee5 th\u1ec3 c\u1ee7a \u1ee9ng d\u1ee5ng. Vi\u1ec7c t\u1ea1o m\u1ed9t Custom View cho ph\u00e9p b\u1ea1n k\u1ebft h\u1ee3p v\u00e0 t\u1ed5 ch\u1ee9c c\u00e1c th\u00e0nh ph\u1ea7n UI nh\u01b0 <\/span><span style=\"font-weight: 400;\">UILabel<\/span><span style=\"font-weight: 400;\">, <\/span><span style=\"font-weight: 400;\">UIButton<\/span><span style=\"font-weight: 400;\">, ho\u1eb7c <\/span><span style=\"font-weight: 400;\">UIImageView<\/span><span style=\"font-weight: 400;\"> trong m\u1ed9t l\u1edbp, gi\u00fap gi\u1ea3m s\u1ef1 tr\u00f9ng l\u1eb7p v\u00e0 t\u0103ng t\u00ednh t\u00e1i s\u1eed d\u1ee5ng c\u1ee7a m\u00e3 ngu\u1ed3n.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Khi n\u00e0o n\u00ean t\u1ea1o m\u1ed9t Custom View?<\/span><\/p>\n<ol>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Khi c\u1ea7n s\u1eed d\u1ee5ng l\u1ea1i m\u1ed9t ph\u1ea7n giao di\u1ec7n ph\u1ee9c t\u1ea1p: N\u1ebfu m\u1ed9t th\u00e0nh ph\u1ea7n UI \u0111\u01b0\u1ee3c d\u00f9ng nhi\u1ec1u l\u1ea7n trong \u1ee9ng d\u1ee5ng v\u00e0 c\u00f3 c\u1ea5u tr\u00fac ph\u1ee9c t\u1ea1p, t\u1ea1o m\u1ed9t Custom View s\u1ebd gi\u00fap b\u1ea1n tr\u00e1nh vi\u1ec7c l\u1eb7p l\u1ea1i c\u00f9ng m\u1ed9t m\u00e3 v\u00e0 d\u1ec5 d\u00e0ng b\u1ea3o tr\u00ec khi c\u00f3 thay \u0111\u1ed5i.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Khi mu\u1ed1n t\u1ea1o c\u00e1c th\u00e0nh ph\u1ea7n giao di\u1ec7n t\u00f9y ch\u1ec9nh: N\u1ebfu \u1ee9ng d\u1ee5ng y\u00eau c\u1ea7u c\u00e1c th\u00e0nh ph\u1ea7n giao di\u1ec7n \u0111\u1ed9c \u0111\u00e1o m\u00e0 <\/span><span style=\"font-weight: 400;\">UIKit<\/span><span style=\"font-weight: 400;\"> kh\u00f4ng cung c\u1ea5p s\u1eb5n (v\u00ed d\u1ee5: bi\u1ec3u \u0111\u1ed3, th\u1ebb th\u00f4ng tin), Custom View l\u00e0 gi\u1ea3i ph\u00e1p ph\u00f9 h\u1ee3p. B\u1ea1n c\u00f3 th\u1ec3 t\u1ef1 do t\u00f9y ch\u1ec9nh giao di\u1ec7n v\u00e0 h\u00e0nh vi c\u1ee7a n\u00f3 theo y\u00eau c\u1ea7u.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Khi c\u1ea7n \u0111\u00f3ng g\u00f3i logic ri\u00eang cho m\u1ed9t th\u00e0nh ph\u1ea7n UI: Custom View cho ph\u00e9p b\u1ea1n \u0111\u00f3ng g\u00f3i c\u1ea3 giao di\u1ec7n l\u1eabn logic x\u1eed l\u00fd ri\u00eang c\u1ee7a m\u1ed9t th\u00e0nh ph\u1ea7n UI v\u00e0o m\u1ed9t l\u1edbp duy nh\u1ea5t, gi\u00fap m\u00e3 ngu\u1ed3n d\u1ec5 \u0111\u1ecdc v\u00e0 qu\u1ea3n l\u00fd h\u01a1n.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Khi mu\u1ed1n t\u00e1ch bi\u1ec7t logic giao di\u1ec7n: N\u1ebfu b\u1ea1n mu\u1ed1n gi\u1eef cho <\/span><span style=\"font-weight: 400;\">UIViewController<\/span><span style=\"font-weight: 400;\"> \u0111\u01a1n gi\u1ea3n h\u01a1n, vi\u1ec7c \u0111\u01b0a c\u00e1c th\u00e0nh ph\u1ea7n UI ph\u1ee9c t\u1ea1p v\u00e0o Custom View s\u1ebd gi\u00fap t\u00e1ch bi\u1ec7t logic giao di\u1ec7n kh\u1ecfi c\u00e1c l\u1edbp \u0111i\u1ec1u khi\u1ec3n, l\u00e0m cho m\u00e3 d\u1ec5 b\u1ea3o tr\u00ec v\u00e0 ki\u1ec3m th\u1eed h\u01a1n.<\/span><\/li>\n<\/ol>\n<h3><strong>L\u00e0m th\u1ebf n\u00e0o \u0111\u1ec3 l\u01b0u v\u00e0 t\u1ea3i \u1ea3nh l\u00ean t\u1eeb th\u01b0 vi\u1ec7n \u1ea3nh (photo library)?<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">C\u00e1c b\u01b0\u1edbc \u0111\u1ec3 l\u01b0u v\u00e0 t\u1ea3i \u1ea3nh t\u1eeb th\u01b0 vi\u1ec7n \u1ea3nh nh\u01b0 sau\u00a0<\/span><\/p>\n<p><span style=\"font-weight: 400;\">B\u01b0\u1edbc 1: UIImagePickerController (iOS 13 tr\u1edf xu\u1ed1ng):<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">C\u1ea5p quy\u1ec1n <\/span><span style=\"font-weight: 400;\">NSPhotoLibraryUsageDescription<\/span><span style=\"font-weight: 400;\"> trong <\/span><span style=\"font-weight: 400;\">Info.plist<\/span><span style=\"font-weight: 400;\">.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">S\u1eed d\u1ee5ng <\/span><span style=\"font-weight: 400;\">UIImagePickerController<\/span><span style=\"font-weight: 400;\"> \u0111\u1ec3 m\u1edf th\u01b0 vi\u1ec7n \u1ea3nh, sau \u0111\u00f3 l\u1ea5y \u1ea3nh qua <\/span><span style=\"font-weight: 400;\">imagePickerController(_:didFinishPickingMediaWithInfo:)<\/span><span style=\"font-weight: 400;\">.<\/span><\/li>\n<\/ul>\n<pre>let imagePicker = UIImagePickerController()\r\nimagePicker.delegate = self\r\nimagePicker.sourceType = .photoLibrary\r\npresent (imagePicker, animated: true)<\/pre>\n<p><span style=\"font-weight: 400;\">B\u01b0\u1edbc 2: PHPickerViewController (iOS 14 tr\u1edf l\u00ean):<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Kh\u00f4ng c\u1ea7n quy\u1ec1n truy c\u1eadp.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">S\u1eed d\u1ee5ng <\/span><span style=\"font-weight: 400;\">PHPickerViewController<\/span><span style=\"font-weight: 400;\"> v\u1edbi <\/span><span style=\"font-weight: 400;\">PHPickerConfiguration<\/span><span style=\"font-weight: 400;\">.<\/span><\/li>\n<\/ul>\n<pre>var config = PHPickerConfiguration()\r\nconfig.selectionLimit = 1\r\nlet picker = PHPickerViewController(configuration: config)\r\npicker.delegate = self\r\npresent (picker, animated: true)<\/pre>\n<p><span style=\"font-weight: 400;\">L\u01b0u \u1ea3nh v\u00e0o th\u01b0 vi\u1ec7n:<\/span><\/p>\n<p><span style=\"font-weight: 400;\">D\u00f9ng <\/span><span style=\"font-weight: 400;\">UIImageWriteToSavedPhotosAlbum<\/span><span style=\"font-weight: 400;\">, \u0111\u1ea3m b\u1ea3o c\u00f3 <\/span><span style=\"font-weight: 400;\">NSPhotoLibraryAddUsageDescription<\/span><span style=\"font-weight: 400;\"> trong <\/span><span style=\"font-weight: 400;\">Info.plist<\/span><span style=\"font-weight: 400;\">.<\/span><\/p>\n<pre>UIImageWriteToSavedPhotosAlbum (image, self, nil, nil)<\/pre>\n<h3><strong>C\u00e1ch tri\u1ec3n khai Dark Mode trong iOS l\u00e0 g\u00ec?<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">\u0110\u1ec3 tri\u1ec3n khai Dark Mode trong iOS, c\u00f3 m\u1ed9t s\u1ed1 c\u00e1ch ti\u1ebfp c\u1eadn \u0111\u1ec3 l\u00e0m cho giao di\u1ec7n t\u1ef1 \u0111\u1ed9ng thay \u0111\u1ed5i theo ch\u1ebf \u0111\u1ed9 s\u00e1ng ho\u1eb7c t\u1ed1i c\u1ee7a h\u1ec7 th\u1ed1ng. Tr\u01b0\u1edbc ti\u00ean, \u01b0u ti\u00ean s\u1eed d\u1ee5ng m\u00e0u h\u1ec7 th\u1ed1ng nh\u01b0 <\/span><span style=\"font-weight: 400;\">.systemBackground<\/span><span style=\"font-weight: 400;\"> ho\u1eb7c <\/span><span style=\"font-weight: 400;\">.label<\/span><span style=\"font-weight: 400;\">, v\u00ec c\u00e1c m\u00e0u n\u00e0y t\u1ef1 \u0111\u1ed9ng th\u00edch \u1ee9ng v\u1edbi Dark Mode m\u00e0 kh\u00f4ng c\u1ea7n c\u1ea5u h\u00ecnh ph\u1ee9c t\u1ea1p.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">N\u1ebfu c\u1ea7n d\u00f9ng m\u00e0u t\u00f9y ch\u1ec9nh, t\u1ea1o c\u00e1c m\u00e0u trong Asset Catalog. Trong Asset Catalog, c\u00f3 t\u00f9y ch\u1ecdn t\u1ea1o c\u00e1c m\u00e0u ri\u00eang bi\u1ec7t cho c\u1ea3 ch\u1ebf \u0111\u1ed9 s\u00e1ng v\u00e0 t\u1ed1i. Vi\u1ec7c n\u00e0y \u0111\u1ea3m b\u1ea3o giao di\u1ec7n s\u1ebd ph\u00f9 h\u1ee3p v\u1edbi t\u1eebng ch\u1ebf \u0111\u1ed9 m\u00e0 kh\u00f4ng c\u1ea7n ch\u1ec9nh s\u1eeda m\u00e3 ngu\u1ed3n nhi\u1ec1u.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">\u0110\u00f4i khi, c\u1ea7n ph\u00e1t hi\u1ec7n v\u00e0 ph\u1ea3n h\u1ed3i khi ch\u1ebf \u0111\u1ed9 s\u00e1ng\/t\u1ed1i thay \u0111\u1ed5i trong l\u00fac \u1ee9ng d\u1ee5ng \u0111ang ch\u1ea1y, s\u1eed d\u1ee5ng ph\u01b0\u01a1ng th\u1ee9c <\/span><span style=\"font-weight: 400;\">traitCollectionDidChange(_:)<\/span><span style=\"font-weight: 400;\">. Ph\u01b0\u01a1ng th\u1ee9c n\u00e0y cho ph\u00e9p ki\u1ec3m tra s\u1ef1 thay \u0111\u1ed5i c\u1ee7a ch\u1ebf \u0111\u1ed9 giao di\u1ec7n v\u00e0 th\u1ef1c hi\u1ec7n c\u00e1c c\u1eadp nh\u1eadt b\u1ed5 sung n\u1ebfu c\u1ea7n.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Cu\u1ed1i c\u00f9ng, n\u1ebfu mu\u1ed1n ki\u1ec3m tra ch\u1ebf \u0111\u1ed9 hi\u1ec7n t\u1ea1i (s\u00e1ng ho\u1eb7c t\u1ed1i), ki\u1ec3m tra thu\u1ed9c t\u00ednh <\/span><span style=\"font-weight: 400;\">userInterfaceStyle<\/span><span style=\"font-weight: 400;\"> c\u1ee7a <\/span><span style=\"font-weight: 400;\">traitCollection<\/span><span style=\"font-weight: 400;\"> trong <\/span><span style=\"font-weight: 400;\">UIViewController<\/span><span style=\"font-weight: 400;\"> ho\u1eb7c <\/span><span style=\"font-weight: 400;\">UIView<\/span><span style=\"font-weight: 400;\">.<\/span><\/p>\n<h3><strong>L\u00e0m th\u1ebf n\u00e0o \u0111\u1ec3 x\u1eed l\u00fd vi\u1ec7c hi\u1ec3n th\u1ecb n\u1ed9i dung khi thi\u1ebft b\u1ecb xoay m\u00e0n h\u00ecnh?<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">Khi thi\u1ebft b\u1ecb xoay m\u00e0n h\u00ecnh, \u0111\u1ec3 \u0111\u1ea3m b\u1ea3o giao di\u1ec7n hi\u1ec3n th\u1ecb \u0111\u00fang, c\u00f3 m\u1ed9t s\u1ed1 c\u00e1ch ti\u1ebfp c\u1eadn ph\u1ed5 bi\u1ebfn. Tr\u01b0\u1edbc ti\u00ean, s\u1eed d\u1ee5ng Auto Layout \u0111\u1ec3 c\u00e1c th\u00e0nh ph\u1ea7n giao di\u1ec7n t\u1ef1 \u0111\u1ed9ng \u0111i\u1ec1u ch\u1ec9nh v\u1ecb tr\u00ed v\u00e0 k\u00edch th\u01b0\u1edbc theo ch\u1ebf \u0111\u1ed9 xoay m\u00e0 kh\u00f4ng c\u1ea7n m\u00e3 ngu\u1ed3n ph\u1ee9c t\u1ea1p. Auto Layout h\u1ed7 tr\u1ee3 r\u1ea5t t\u1ed1t cho vi\u1ec7c n\u00e0y, v\u00ec n\u00f3 cho ph\u00e9p giao di\u1ec7n ph\u1ea3n h\u1ed3i linh ho\u1ea1t v\u1edbi nhi\u1ec1u k\u00edch th\u01b0\u1edbc m\u00e0n h\u00ecnh.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">N\u1ebfu c\u1ea7n th\u1ef1c hi\u1ec7n t\u00f9y ch\u1ec9nh c\u1ee5 th\u1ec3 khi xoay m\u00e0n h\u00ecnh, s\u1eed d\u1ee5ng ph\u01b0\u01a1ng th\u1ee9c <\/span><span style=\"font-weight: 400;\">viewWillTransition(to:with:)<\/span><span style=\"font-weight: 400;\"> trong <\/span><span style=\"font-weight: 400;\">UIViewController<\/span><span style=\"font-weight: 400;\">. Ph\u01b0\u01a1ng th\u1ee9c n\u00e0y cung c\u1ea5p <\/span><span style=\"font-weight: 400;\">size<\/span><span style=\"font-weight: 400;\"> m\u1edbi v\u00e0 cho ph\u00e9p t\u00f4i \u0111i\u1ec1u ch\u1ec9nh n\u1ed9i dung ho\u1eb7c b\u1ed1 c\u1ee5c m\u1ed9t c\u00e1ch linh ho\u1ea1t tr\u01b0\u1edbc khi chuy\u1ec3n \u0111\u1ed5i ho\u00e0n t\u1ea5t.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Ngo\u00e0i ra, ki\u1ec3m tra <\/span><span style=\"font-weight: 400;\">UIDevice.current.orientation<\/span><span style=\"font-weight: 400;\"> \u0111\u1ec3 x\u00e1c \u0111\u1ecbnh h\u01b0\u1edbng thi\u1ebft b\u1ecb hi\u1ec7n t\u1ea1i n\u1ebfu c\u1ea7n th\u1ef1c hi\u1ec7n c\u00e1c thay \u0111\u1ed5i chi ti\u1ebft d\u1ef1a tr\u00ean h\u01b0\u1edbng c\u1ee5 th\u1ec3 (nh\u01b0 hi\u1ec3n th\u1ecb chi ti\u1ebft h\u01a1n \u1edf ch\u1ebf \u0111\u1ed9 ngang).<\/span><\/p>\n<h2><span class=\"ez-toc-section\" id=\"Cac_cau_hoi_phong_van_lien_quan_den_toi_uu_hoa_hieu_nang\"><\/span><strong>C\u00e1c c\u00e2u h\u1ecfi ph\u1ecfng v\u1ea5n li\u00ean quan \u0111\u1ebfn t\u1ed1i \u01b0u ho\u00e1 hi\u1ec7u n\u0103ng\u00a0<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n<h3><strong>L\u00e0m th\u1ebf n\u00e0o \u0111\u1ec3 t\u1ed1i \u01b0u h\u00f3a vi\u1ec7c cu\u1ed9n trong UITableView ho\u1eb7c UICollectionView?<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">\u0110\u1ec3 t\u1ed1i \u01b0u h\u00f3a vi\u1ec7c cu\u1ed9n trong <\/span><span style=\"font-weight: 400;\">UITableView<\/span><span style=\"font-weight: 400;\"> ho\u1eb7c <\/span><span style=\"font-weight: 400;\">UICollectionView<\/span><span style=\"font-weight: 400;\">, t\u00f4i th\u01b0\u1eddng \u00e1p d\u1ee5ng m\u1ed9t s\u1ed1 k\u1ef9 thu\u1eadt sau:<\/span><\/p>\n<ol>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>S\u1eed d\u1ee5ng Reusable Cells<\/b><span style=\"font-weight: 400;\">: \u0110\u1ea3m b\u1ea3o s\u1eed d\u1ee5ng <\/span><span style=\"font-weight: 400;\">dequeueReusableCell(withIdentifier:for:)<\/span><span style=\"font-weight: 400;\"> \u0111\u1ec3 t\u00e1i s\u1eed d\u1ee5ng c\u00e1c \u00f4. Vi\u1ec7c n\u00e0y gi\u00fap gi\u1ea3m thi\u1ec3u vi\u1ec7c t\u1ea1o m\u1edbi c\u00e1c \u00f4 v\u00e0 c\u1ea3i thi\u1ec7n hi\u1ec7u su\u1ea5t khi cu\u1ed9n.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>Ch\u1ec9 t\u1ea3i d\u1eef li\u1ec7u c\u1ea7n thi\u1ebft<\/b><span style=\"font-weight: 400;\">: \u00c1p d\u1ee5ng ph\u00e2n trang ho\u1eb7c t\u1ea3i d\u1eef li\u1ec7u khi c\u1ea7n thi\u1ebft \u0111\u1ec3 kh\u00f4ng t\u1ea3i to\u00e0n b\u1ed9 d\u1eef li\u1ec7u ngay t\u1eeb \u0111\u1ea7u, \u0111i\u1ec1u n\u00e0y gi\u00fap gi\u1ea3m t\u1ea3i cho b\u1ed9 nh\u1edb.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>Gi\u1ea3m thi\u1ec3u c\u00f4ng vi\u1ec7c trong <\/b><b>cellForRowAt<\/b><b> ho\u1eb7c <\/b><b>cellForItemAt<\/b><span style=\"font-weight: 400;\">: Ch\u1ec9 th\u1ef1c hi\u1ec7n c\u00e1c thao t\u00e1c nh\u1eb9 nh\u00e0ng trong c\u00e1c ph\u01b0\u01a1ng th\u1ee9c n\u00e0y. N\u1ebfu c\u1ea7n t\u00ednh to\u00e1n n\u1eb7ng, t\u00f4i s\u1ebd l\u00e0m \u0111i\u1ec1u \u0111\u00f3 tr\u01b0\u1edbc v\u00e0 l\u01b0u tr\u1eef k\u1ebft qu\u1ea3.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>S\u1eed d\u1ee5ng <\/b><b>prefetching<\/b><span style=\"font-weight: 400;\">: B\u1eadt t\u00ednh n\u0103ng prefetching \u0111\u1ec3 t\u1ea3i tr\u01b0\u1edbc d\u1eef li\u1ec7u cho c\u00e1c \u00f4 m\u00e0 ng\u01b0\u1eddi d\u00f9ng c\u00f3 kh\u1ea3 n\u0103ng cu\u1ed9n \u0111\u1ebfn, \u0111i\u1ec1u n\u00e0y gi\u00fap c\u1ea3i thi\u1ec7n tr\u1ea3i nghi\u1ec7m cu\u1ed9n.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>T\u1ed1i \u01b0u h\u00f3a h\u00ecnh \u1ea3nh<\/b><span style=\"font-weight: 400;\">: Khi l\u00e0m vi\u1ec7c v\u1edbi h\u00ecnh \u1ea3nh, t\u00f4i s\u1ebd s\u1eed d\u1ee5ng c\u00e1c th\u01b0 vi\u1ec7n nh\u01b0 <\/span><span style=\"font-weight: 400;\">SDWebImage<\/span><span style=\"font-weight: 400;\"> \u0111\u1ec3 t\u1ea3i h\u00ecnh \u1ea3nh kh\u00f4ng \u0111\u1ed3ng b\u1ed9 v\u00e0 cache h\u00ecnh \u1ea3nh. C\u0169ng n\u00ean \u0111\u1ea3m b\u1ea3o k\u00edch th\u01b0\u1edbc h\u00ecnh \u1ea3nh \u0111\u01b0\u1ee3c t\u1ed1i \u01b0u h\u00f3a \u0111\u1ec3 ph\u00f9 h\u1ee3p v\u1edbi k\u00edch th\u01b0\u1edbc c\u1ee7a \u00f4.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>T\u1eaft c\u00e1c hi\u1ec7u \u1ee9ng kh\u00f4ng c\u1ea7n thi\u1ebft<\/b><span style=\"font-weight: 400;\">: Gi\u1ea3m thi\u1ec3u c\u00e1c hi\u1ec7u \u1ee9ng animation ph\u1ee9c t\u1ea1p ho\u1eb7c kh\u00f4ng c\u1ea7n thi\u1ebft khi cu\u1ed9n \u0111\u1ec3 tr\u00e1nh l\u00e0m ch\u1eadm hi\u1ec7u su\u1ea5t.<\/span><\/li>\n<\/ol>\n<p><span style=\"font-weight: 400;\">B\u1eb1ng c\u00e1ch \u00e1p d\u1ee5ng nh\u1eefng k\u1ef9 thu\u1eadt n\u00e0y, t\u00f4i c\u00f3 th\u1ec3 c\u1ea3i thi\u1ec7n hi\u1ec7u su\u1ea5t v\u00e0 tr\u1ea3i nghi\u1ec7m ng\u01b0\u1eddi d\u00f9ng khi cu\u1ed9n trong <\/span><span style=\"font-weight: 400;\">UITableView<\/span><span style=\"font-weight: 400;\"> ho\u1eb7c <\/span><span style=\"font-weight: 400;\">UICollectionView<\/span><span style=\"font-weight: 400;\">.<\/span><\/p>\n<h3><strong>Instruments l\u00e0 g\u00ec v\u00e0 l\u00e0m th\u1ebf n\u00e0o \u0111\u1ec3 s\u1eed d\u1ee5ng n\u00f3 \u0111\u1ec3 t\u00ecm ra c\u00e1c v\u1ea5n \u0111\u1ec1 v\u1ec1 hi\u1ec7u su\u1ea5t trong \u1ee9ng d\u1ee5ng iOS?<\/strong><\/h3>\n<p><b>Instruments<\/b><span style=\"font-weight: 400;\"> l\u00e0 m\u1ed9t c\u00f4ng c\u1ee5 m\u1ea1nh m\u1ebd trong b\u1ed9 c\u00f4ng c\u1ee5 Xcode, cho ph\u00e9p l\u1eadp tr\u00ecnh vi\u00ean theo d\u00f5i v\u00e0 ph\u00e2n t\u00edch hi\u1ec7u su\u1ea5t c\u1ee7a \u1ee9ng d\u1ee5ng iOS. Instruments gi\u00fap ph\u00e1t hi\u1ec7n c\u00e1c v\u1ea5n \u0111\u1ec1 nh\u01b0 r\u00f2 r\u1ec9 b\u1ed9 nh\u1edb, th\u1eddi gian th\u1ef1c thi c\u1ee7a m\u00e3, v\u00e0 c\u00e1c v\u1ea5n \u0111\u1ec1 li\u00ean quan \u0111\u1ebfn CPU, GPU v\u00e0 m\u1ea1ng.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">\u0110\u1ec3 s\u1eed d\u1ee5ng Instruments, t\u00f4i th\u1ef1c hi\u1ec7n theo c\u00e1c b\u01b0\u1edbc sau:<\/span><\/p>\n<ol>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>M\u1edf Instruments<\/b><span style=\"font-weight: 400;\">: T\u1eeb Xcode, ch\u1ecdn <\/span><span style=\"font-weight: 400;\">Product<\/span><span style=\"font-weight: 400;\"> -&gt; <\/span><span style=\"font-weight: 400;\">Profile<\/span><span style=\"font-weight: 400;\"> ho\u1eb7c nh\u1ea5n <\/span><span style=\"font-weight: 400;\">Command + I<\/span><span style=\"font-weight: 400;\">. Xcode s\u1ebd bi\u00ean d\u1ecbch \u1ee9ng d\u1ee5ng v\u00e0 m\u1edf Instruments.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>Ch\u1ecdn Template<\/b><span style=\"font-weight: 400;\">: Ch\u1ecdn m\u1ed9t template ph\u00f9 h\u1ee3p v\u1edbi v\u1ea5n \u0111\u1ec1 b\u1ea1n mu\u1ed1n ph\u00e2n t\u00edch, v\u00ed d\u1ee5:<\/span>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><b>Time Profiler<\/b><span style=\"font-weight: 400;\"> \u0111\u1ec3 theo d\u00f5i hi\u1ec7u su\u1ea5t CPU.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><b>Allocations<\/b><span style=\"font-weight: 400;\"> \u0111\u1ec3 ph\u00e2n t\u00edch vi\u1ec7c c\u1ea5p ph\u00e1t b\u1ed9 nh\u1edb.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><b>Leaks<\/b><span style=\"font-weight: 400;\"> \u0111\u1ec3 t\u00ecm c\u00e1c r\u00f2 r\u1ec9 b\u1ed9 nh\u1edb.<\/span><\/li>\n<\/ul>\n<\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>Ghi l\u1ea1i ho\u1ea1t \u0111\u1ed9ng<\/b><span style=\"font-weight: 400;\">: Nh\u1ea5n n\u00fat ghi \u0111\u1ec3 b\u1eaft \u0111\u1ea7u theo d\u00f5i. Th\u1ef1c hi\u1ec7n c\u00e1c thao t\u00e1c trong \u1ee9ng d\u1ee5ng m\u00e0 b\u1ea1n nghi ng\u1edd c\u00f3 v\u1ea5n \u0111\u1ec1 v\u1ec1 hi\u1ec7u su\u1ea5t.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>Ph\u00e2n t\u00edch d\u1eef li\u1ec7u<\/b><span style=\"font-weight: 400;\">: Sau khi d\u1eebng ghi, t\u00f4i s\u1ebd ph\u00e2n t\u00edch c\u00e1c d\u1eef li\u1ec7u \u0111\u00e3 thu th\u1eadp:<\/span>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><b>Time Profiler<\/b><span style=\"font-weight: 400;\"> cho th\u1ea5y c\u00e1c ph\u01b0\u01a1ng th\u1ee9c n\u00e0o ti\u00eau t\u1ed1n nhi\u1ec1u th\u1eddi gian CPU.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><b>Allocations<\/b><span style=\"font-weight: 400;\"> cho bi\u1ebft c\u00e1c \u0111\u1ed1i t\u01b0\u1ee3ng n\u00e0o \u0111ang chi\u1ebfm nhi\u1ec1u b\u1ed9 nh\u1edb.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><b>Leaks<\/b><span style=\"font-weight: 400;\"> ch\u1ec9 ra c\u00e1c r\u00f2 r\u1ec9 b\u1ed9 nh\u1edb n\u1ebfu c\u00f3.<\/span><\/li>\n<\/ul>\n<\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>T\u1ed1i \u01b0u h\u00f3a<\/b><span style=\"font-weight: 400;\">: D\u1ef1a tr\u00ean th\u00f4ng tin t\u1eeb Instruments, t\u00f4i s\u1ebd x\u00e1c \u0111\u1ecbnh c\u00e1c \u0111i\u1ec3m c\u1ea7n t\u1ed1i \u01b0u h\u00f3a v\u00e0 ti\u1ebfn h\u00e0nh c\u1ea3i thi\u1ec7n m\u00e3 ngu\u1ed3n ho\u1eb7c c\u00e1c c\u1ea5u tr\u00fac d\u1eef li\u1ec7u \u0111\u1ec3 n\u00e2ng cao hi\u1ec7u su\u1ea5t.<\/span><\/li>\n<\/ol>\n<p><span style=\"font-weight: 400;\">S\u1eed d\u1ee5ng Instruments m\u1ed9t c\u00e1ch h\u1ee3p l\u00fd gi\u00fap t\u00f4i theo d\u00f5i v\u00e0 t\u1ed1i \u01b0u h\u00f3a hi\u1ec7u su\u1ea5t \u1ee9ng d\u1ee5ng m\u1ed9t c\u00e1ch hi\u1ec7u qu\u1ea3.<\/span><\/p>\n<h3><strong>@escaping l\u00e0 g\u00ec trong Swift? Khi n\u00e0o n\u00ean s\u1eed d\u1ee5ng?<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">Trong Swift, t\u1eeb kh\u00f3a <\/span><span style=\"font-weight: 400;\">@escaping<\/span><span style=\"font-weight: 400;\"> \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng \u0111\u1ec3 ch\u1ec9 \u0111\u1ecbnh r\u1eb1ng m\u1ed9t closure c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c g\u1ecdi sau khi h\u00e0m m\u00e0 n\u00f3 \u0111\u01b0\u1ee3c truy\u1ec1n v\u00e0o \u0111\u00e3 ho\u00e0n th\u00e0nh. \u0110i\u1ec1u n\u00e0y c\u00f3 ngh\u0129a l\u00e0 closure \u0111\u00f3 &#8220;tho\u00e1t&#8221; kh\u1ecfi v\u00f2ng \u0111\u1eddi c\u1ee7a h\u00e0m.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Khi b\u1ea1n \u0111\u1ecbnh ngh\u0129a m\u1ed9t closure l\u00e0 <\/span><span style=\"font-weight: 400;\">@escaping<\/span><span style=\"font-weight: 400;\">, b\u1ea1n cho Swift bi\u1ebft r\u1eb1ng closure n\u00e0y c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c l\u01b0u tr\u1eef v\u00e0 g\u1ecdi sau, ch\u1eb3ng h\u1ea1n nh\u01b0 trong c\u00e1c callback ho\u1eb7c khi x\u1eed l\u00fd b\u1ea5t \u0111\u1ed3ng b\u1ed9.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Khi n\u00e0o n\u00ean s\u1eed d\u1ee5ng <\/span><span style=\"font-weight: 400;\">@escaping<\/span><span style=\"font-weight: 400;\">:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>Callback trong h\u00e0m b\u1ea5t \u0111\u1ed3ng b\u1ed9<\/b><span style=\"font-weight: 400;\">: Khi b\u1ea1n truy\u1ec1n m\u1ed9t closure v\u00e0o m\u1ed9t h\u00e0m th\u1ef1c hi\u1ec7n c\u00e1c t\u00e1c v\u1ee5 b\u1ea5t \u0111\u1ed3ng b\u1ed9, nh\u01b0 g\u1ecdi API ho\u1eb7c th\u1ef1c hi\u1ec7n ho\u1ea1t \u0111\u1ed9ng n\u1ec1n, closure n\u00e0y c\u1ea7n \u0111\u01b0\u1ee3c \u0111\u00e1nh d\u1ea5u l\u00e0 <\/span><span style=\"font-weight: 400;\">@escaping<\/span><span style=\"font-weight: 400;\"> v\u00ec n\u00f3 s\u1ebd \u0111\u01b0\u1ee3c g\u1ecdi sau khi h\u00e0m ho\u00e0n t\u1ea5t.<\/span><\/li>\n<\/ul>\n<pre>func fetchData(completion: @escaping (Data?) -&gt; Void) {\r\n  \/\/ Th\u1ef1c hi\u1ec7n g\u1ecdi API b\u1ea5t \u0111\u1ed3ng b\u1ed9 DispatchQueue.global().async {\r\n  DispatchQueue.global().async {\r\n    let data = ... \/\/ t\u1ea3i d\u1eef li\u1ec7u\r\n    completion(data) \/\/ g\u1ecdi closure sau khi ho\u00e0n th\u00e0nh\r\n  }\r\n}<\/pre>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>L\u01b0u closure trong thu\u1ed9c t\u00ednh<\/b><span style=\"font-weight: 400;\">: N\u1ebfu b\u1ea1n mu\u1ed1n l\u01b0u closure v\u00e0o thu\u1ed9c t\u00ednh c\u1ee7a m\u1ed9t l\u1edbp ho\u1eb7c struct, b\u1ea1n c\u1ea7n \u0111\u00e1nh d\u1ea5u closure \u0111\u00f3 l\u00e0 <\/span><span style=\"font-weight: 400;\">@escaping<\/span><span style=\"font-weight: 400;\"> v\u00ec n\u00f3 s\u1ebd \u0111\u01b0\u1ee3c g\u1ecdi sau khi h\u00e0m ho\u00e0n t\u1ea5t.<\/span><\/li>\n<\/ul>\n<pre>class MyClass{\r\n  var completionHandler: ((String) -&gt; Void)?\r\n\r\n  func doSomething (completion: @escaping (String) -&gt; Void) {\r\n    self.completionHandler = completion \/\/ l\u01b0u closure\r\n  }\r\n}<\/pre>\n<h3><strong>L\u00e0m th\u1ebf n\u00e0o \u0111\u1ec3 gi\u1ea3m thi\u1ec3u vi\u1ec7c s\u1eed d\u1ee5ng b\u1ed9 nh\u1edb khi x\u1eed l\u00fd h\u00ecnh \u1ea3nh l\u1edbn trong iOS?<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">\u0110\u1ec3 gi\u1ea3m thi\u1ec3u vi\u1ec7c s\u1eed d\u1ee5ng b\u1ed9 nh\u1edb khi x\u1eed l\u00fd h\u00ecnh \u1ea3nh l\u1edbn trong iOS, t\u00f4i th\u01b0\u1eddng \u00e1p d\u1ee5ng c\u00e1c ph\u01b0\u01a1ng ph\u00e1p sau:<\/span><\/p>\n<ol>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>S\u1eed d\u1ee5ng h\u00ecnh \u1ea3nh c\u00f3 \u0111\u1ed9 ph\u00e2n gi\u1ea3i th\u1ea5p h\u01a1n<\/b><span style=\"font-weight: 400;\">: Khi t\u1ea3i h\u00ecnh \u1ea3nh, t\u00f4i s\u1ebd s\u1eed d\u1ee5ng phi\u00ean b\u1ea3n h\u00ecnh \u1ea3nh c\u00f3 \u0111\u1ed9 ph\u00e2n gi\u1ea3i th\u1ea5p h\u01a1n thay v\u00ec h\u00ecnh \u1ea3nh g\u1ed1c. \u0110i\u1ec1u n\u00e0y gi\u00fap gi\u1ea3m k\u00edch th\u01b0\u1edbc b\u1ed9 nh\u1edb khi h\u00ecnh \u1ea3nh \u0111\u01b0\u1ee3c hi\u1ec3n th\u1ecb.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>Lazy Loading<\/b><span style=\"font-weight: 400;\">: T\u1ea3i h\u00ecnh \u1ea3nh khi c\u1ea7n thi\u1ebft thay v\u00ec t\u1ea3i t\u1ea5t c\u1ea3 h\u00ecnh \u1ea3nh c\u00f9ng l\u00fac. T\u00f4i c\u00f3 th\u1ec3 s\u1eed d\u1ee5ng <\/span><span style=\"font-weight: 400;\">UIImageView<\/span><span style=\"font-weight: 400;\"> v\u1edbi ph\u01b0\u01a1ng th\u1ee9c t\u1ea3i h\u00ecnh \u1ea3nh kh\u00f4ng \u0111\u1ed3ng b\u1ed9 \u0111\u1ec3 tr\u00e1nh l\u00e0m \u0111\u00f4ng \u0111\u00fac b\u1ed9 nh\u1edb.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>S\u1eed d\u1ee5ng Cache<\/b><span style=\"font-weight: 400;\">: S\u1eed d\u1ee5ng b\u1ed9 nh\u1edb \u0111\u1ec7m \u0111\u1ec3 l\u01b0u tr\u1eef h\u00ecnh \u1ea3nh \u0111\u00e3 t\u1ea3i, nh\u01b0 <\/span><span style=\"font-weight: 400;\">NSCache<\/span><span style=\"font-weight: 400;\"> ho\u1eb7c th\u01b0 vi\u1ec7n b\u00ean ngo\u00e0i nh\u01b0 <\/span><span style=\"font-weight: 400;\">SDWebImage<\/span><span style=\"font-weight: 400;\">. \u0110i\u1ec1u n\u00e0y gi\u00fap tr\u00e1nh vi\u1ec7c t\u1ea3i l\u1ea1i h\u00ecnh \u1ea3nh t\u1eeb ngu\u1ed3n g\u1ed1c m\u1ed7i khi c\u1ea7n hi\u1ec3n th\u1ecb.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>Gi\u1ea3m k\u00edch th\u01b0\u1edbc h\u00ecnh \u1ea3nh khi hi\u1ec3n th\u1ecb<\/b><span style=\"font-weight: 400;\">: Tr\u01b0\u1edbc khi hi\u1ec3n th\u1ecb h\u00ecnh \u1ea3nh, t\u00f4i s\u1ebd thay \u0111\u1ed5i k\u00edch th\u01b0\u1edbc n\u00f3 sao cho ph\u00f9 h\u1ee3p v\u1edbi k\u00edch th\u01b0\u1edbc c\u1ee7a <\/span><span style=\"font-weight: 400;\">UIImageView<\/span><span style=\"font-weight: 400;\"> ho\u1eb7c th\u00e0nh ph\u1ea7n hi\u1ec3n th\u1ecb. Vi\u1ec7c n\u00e0y c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c th\u1ef1c hi\u1ec7n th\u00f4ng qua c\u00e1c th\u01b0 vi\u1ec7n nh\u01b0 <\/span><span style=\"font-weight: 400;\">ImageMagick<\/span><span style=\"font-weight: 400;\"> ho\u1eb7c c\u00e1c ph\u01b0\u01a1ng th\u1ee9c t\u00edch h\u1ee3p s\u1eb5n.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>S\u1eed d\u1ee5ng <\/b><b>CGImage<\/b><b> thay v\u00ec <\/b><b>UIImage<\/b><span style=\"font-weight: 400;\">: Khi l\u00e0m vi\u1ec7c v\u1edbi h\u00ecnh \u1ea3nh l\u1edbn, t\u00f4i c\u00f3 th\u1ec3 s\u1eed d\u1ee5ng <\/span><span style=\"font-weight: 400;\">CGImage<\/span><span style=\"font-weight: 400;\"> \u0111\u1ec3 x\u1eed l\u00fd tr\u1ef1c ti\u1ebfp tr\u00ean c\u00e1c h\u00ecnh \u1ea3nh m\u00e0 kh\u00f4ng c\u1ea7n ph\u1ea3i chuy\u1ec3n \u0111\u1ed5i sang <\/span><span style=\"font-weight: 400;\">UIImage<\/span><span style=\"font-weight: 400;\">, \u0111i\u1ec1u n\u00e0y c\u00f3 th\u1ec3 ti\u1ebft ki\u1ec7m b\u1ed9 nh\u1edb.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>X\u1eed l\u00fd h\u00ecnh \u1ea3nh trong background<\/b><span style=\"font-weight: 400;\">: Khi c\u1ea7n x\u1eed l\u00fd h\u00ecnh \u1ea3nh, t\u00f4i th\u01b0\u1eddng th\u1ef1c hi\u1ec7n n\u00f3 trong background thread \u0111\u1ec3 kh\u00f4ng l\u00e0m \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn giao di\u1ec7n ng\u01b0\u1eddi d\u00f9ng.<\/span><\/li>\n<\/ol>\n<p><span style=\"font-weight: 400;\">B\u1eb1ng c\u00e1ch \u00e1p d\u1ee5ng nh\u1eefng ph\u01b0\u01a1ng ph\u00e1p n\u00e0y, t\u00f4i c\u00f3 th\u1ec3 gi\u1ea3m thi\u1ec3u vi\u1ec7c s\u1eed d\u1ee5ng b\u1ed9 nh\u1edb v\u00e0 c\u1ea3i thi\u1ec7n hi\u1ec7u su\u1ea5t c\u1ee7a \u1ee9ng d\u1ee5ng khi x\u1eed l\u00fd h\u00ecnh \u1ea3nh l\u1edbn.<\/span><\/p>\n<h3><strong>Ph\u00e2n bi\u1ec7t gi\u1eefa Synchronous v\u00e0 Asynchronous<\/strong><span style=\"font-weight: 400;\"><strong> trong giao ti\u1ebfp client v\u00e0 server<\/strong><\/span><\/h3>\n<p><b>Synchronous<\/b><b> (\u0110\u1ed3ng b\u1ed9)<\/b><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>\u0110\u1ecbnh ngh\u0129a<\/b><span style=\"font-weight: 400;\">: Trong giao ti\u1ebfp \u0111\u1ed3ng b\u1ed9, client s\u1ebd g\u1eedi y\u00eau c\u1ea7u \u0111\u1ebfn server v\u00e0 ch\u1edd \u0111\u1ee3i ph\u1ea3n h\u1ed3i tr\u01b0\u1edbc khi ti\u1ebfp t\u1ee5c th\u1ef1c hi\u1ec7n b\u1ea5t k\u1ef3 thao t\u00e1c n\u00e0o kh\u00e1c. \u0110i\u1ec1u n\u00e0y c\u00f3 ngh\u0129a l\u00e0 client s\u1ebd &#8220;b\u1ecb ch\u1eb7n&#8221; cho \u0111\u1ebfn khi server tr\u1ea3 v\u1ec1 k\u1ebft qu\u1ea3.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>\u01afu \u0111i\u1ec3m<\/b><span style=\"font-weight: 400;\">:<\/span>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">\u0110\u01a1n gi\u1ea3n v\u00e0 d\u1ec5 hi\u1ec3u, v\u00ec lu\u1ed3ng th\u1ef1c thi l\u00e0 tu\u1ea7n t\u1ef1.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">Ph\u1ea3n h\u1ed3i nh\u1eadn \u0111\u01b0\u1ee3c ngay l\u1eadp t\u1ee9c sau khi y\u00eau c\u1ea7u \u0111\u01b0\u1ee3c g\u1eedi.<\/span><\/li>\n<\/ul>\n<\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>Nh\u01b0\u1ee3c \u0111i\u1ec3m<\/b><span style=\"font-weight: 400;\">:<\/span>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">C\u00f3 th\u1ec3 g\u00e2y ra tr\u1ea3i nghi\u1ec7m ng\u01b0\u1eddi d\u00f9ng kh\u00f4ng t\u1ed1t, v\u00ec n\u1ebfu server ph\u1ea3n h\u1ed3i ch\u1eadm, client s\u1ebd kh\u00f4ng th\u1ec3 th\u1ef1c hi\u1ec7n b\u1ea5t k\u1ef3 thao t\u00e1c n\u00e0o kh\u00e1c trong th\u1eddi gian ch\u1edd \u0111\u1ee3i.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">Kh\u00f3 m\u1edf r\u1ed9ng, \u0111\u1eb7c bi\u1ec7t trong tr\u01b0\u1eddng h\u1ee3p c\u00f3 nhi\u1ec1u y\u00eau c\u1ea7u t\u1eeb nhi\u1ec1u client c\u00f9ng m\u1ed9t l\u00fac.<\/span><\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p><b>Asynchronous (B\u1ea5t \u0111\u1ed3ng b\u1ed9)<\/b><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>\u0110\u1ecbnh ngh\u0129a<\/b><span style=\"font-weight: 400;\">: Trong giao ti\u1ebfp b\u1ea5t \u0111\u1ed3ng b\u1ed9, client g\u1eedi y\u00eau c\u1ea7u \u0111\u1ebfn server v\u00e0 kh\u00f4ng c\u1ea7n ch\u1edd \u0111\u1ee3i ph\u1ea3n h\u1ed3i ngay l\u1eadp t\u1ee9c. Thay v\u00e0o \u0111\u00f3, client c\u00f3 th\u1ec3 ti\u1ebfp t\u1ee5c th\u1ef1c hi\u1ec7n c\u00e1c t\u00e1c v\u1ee5 kh\u00e1c trong khi \u0111ang ch\u1edd ph\u1ea3n h\u1ed3i t\u1eeb server. Ph\u1ea3n h\u1ed3i s\u1ebd \u0111\u01b0\u1ee3c x\u1eed l\u00fd th\u00f4ng qua callback ho\u1eb7c promises sau khi server tr\u1ea3 v\u1ec1 d\u1eef li\u1ec7u.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>\u01afu \u0111i\u1ec3m<\/b><span style=\"font-weight: 400;\">:<\/span>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">C\u1ea3i thi\u1ec7n tr\u1ea3i nghi\u1ec7m ng\u01b0\u1eddi d\u00f9ng, v\u00ec client kh\u00f4ng b\u1ecb ch\u1eb7n v\u00e0 c\u00f3 th\u1ec3 th\u1ef1c hi\u1ec7n nhi\u1ec1u thao t\u00e1c kh\u00e1c trong khi ch\u1edd ph\u1ea3n h\u1ed3i.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">Hi\u1ec7u su\u1ea5t t\u1ed1t h\u01a1n trong tr\u01b0\u1eddng h\u1ee3p c\u00f3 nhi\u1ec1u y\u00eau c\u1ea7u, v\u00ec client c\u00f3 th\u1ec3 g\u1eedi nhi\u1ec1u y\u00eau c\u1ea7u m\u00e0 kh\u00f4ng c\u1ea7n ch\u1edd ph\u1ea3n h\u1ed3i t\u1eeb t\u1eebng y\u00eau c\u1ea7u.<\/span><\/li>\n<\/ul>\n<\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>Nh\u01b0\u1ee3c \u0111i\u1ec3m<\/b><span style=\"font-weight: 400;\">:<\/span>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">Ph\u1ee9c t\u1ea1p h\u01a1n trong vi\u1ec7c qu\u1ea3n l\u00fd lu\u1ed3ng th\u1ef1c thi v\u00e0 x\u1eed l\u00fd callback.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">C\u00f3 th\u1ec3 d\u1eabn \u0111\u1ebfn &#8220;callback hell&#8221; n\u1ebfu kh\u00f4ng \u0111\u01b0\u1ee3c t\u1ed5 ch\u1ee9c t\u1ed1t, l\u00e0m cho m\u00e3 kh\u00f3 \u0111\u1ecdc v\u00e0 b\u1ea3o tr\u00ec.<\/span><\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<h3><strong>L\u00e0m th\u1ebf n\u00e0o \u0111\u1ec3 \u0111\u1ea3m b\u1ea3o an to\u00e0n d\u1eef li\u1ec7u ng\u01b0\u1eddi d\u00f9ng trong \u1ee9ng d\u1ee5ng iOS?<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">\u0110\u1ec3 \u0111\u1ea3m b\u1ea3o an to\u00e0n d\u1eef li\u1ec7u ng\u01b0\u1eddi d\u00f9ng trong \u1ee9ng d\u1ee5ng iOS, t\u00f4i th\u01b0\u1eddng \u00e1p d\u1ee5ng c\u00e1c ph\u01b0\u01a1ng ph\u00e1p sau:<\/span><\/p>\n<ol>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>M\u00e3 h\u00f3a d\u1eef li\u1ec7u<\/b><span style=\"font-weight: 400;\">:<\/span>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">S\u1eed d\u1ee5ng m\u00e3 h\u00f3a m\u1ea1nh m\u1ebd (nh\u01b0 AES-256) \u0111\u1ec3 b\u1ea3o v\u1ec7 d\u1eef li\u1ec7u nh\u1ea1y c\u1ea3m tr\u01b0\u1edbc khi l\u01b0u tr\u1eef ho\u1eb7c truy\u1ec1n t\u1ea3i. \u0110i\u1ec1u n\u00e0y gi\u00fap \u0111\u1ea3m b\u1ea3o r\u1eb1ng ngay c\u1ea3 khi d\u1eef li\u1ec7u b\u1ecb r\u00f2 r\u1ec9, n\u00f3 c\u0169ng kh\u00f4ng th\u1ec3 \u0111\u01b0\u1ee3c truy c\u1eadp d\u1ec5 d\u00e0ng.<\/span><\/li>\n<\/ul>\n<\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>S\u1eed d\u1ee5ng Keychain<\/b><span style=\"font-weight: 400;\">:<\/span>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">L\u01b0u tr\u1eef th\u00f4ng tin nh\u1ea1y c\u1ea3m nh\u01b0 m\u1eadt kh\u1ea9u v\u00e0 m\u00e3 x\u00e1c th\u1ef1c trong Keychain c\u1ee7a iOS. Keychain cung c\u1ea5p m\u1ed9t c\u00e1ch an to\u00e0n \u0111\u1ec3 l\u01b0u tr\u1eef th\u00f4ng tin nh\u1ea1y c\u1ea3m v\u00e0 t\u1ef1 \u0111\u1ed9ng m\u00e3 h\u00f3a d\u1eef li\u1ec7u.<\/span><\/li>\n<\/ul>\n<\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>X\u00e1c th\u1ef1c ng\u01b0\u1eddi d\u00f9ng<\/b><span style=\"font-weight: 400;\">:<\/span>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">S\u1eed d\u1ee5ng ph\u01b0\u01a1ng th\u1ee9c x\u00e1c th\u1ef1c m\u1ea1nh m\u1ebd, ch\u1eb3ng h\u1ea1n nh\u01b0 x\u00e1c th\u1ef1c hai y\u1ebfu t\u1ed1 (2FA), \u0111\u1ec3 t\u0103ng c\u01b0\u1eddng b\u1ea3o m\u1eadt cho t\u00e0i kho\u1ea3n ng\u01b0\u1eddi d\u00f9ng.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">T\u00edch h\u1ee3p v\u1edbi c\u00e1c d\u1ecbch v\u1ee5 nh\u01b0 Firebase Authentication ho\u1eb7c OAuth \u0111\u1ec3 qu\u1ea3n l\u00fd v\u00e0 b\u1ea3o v\u1ec7 th\u00f4ng tin x\u00e1c th\u1ef1c.<\/span><\/li>\n<\/ul>\n<\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>Ki\u1ec3m tra quy\u1ec1n truy c\u1eadp<\/b><span style=\"font-weight: 400;\">:<\/span>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">Th\u1ef1c hi\u1ec7n ki\u1ec3m tra quy\u1ec1n truy c\u1eadp nghi\u00eam ng\u1eb7t \u0111\u1ec3 \u0111\u1ea3m b\u1ea3o r\u1eb1ng ng\u01b0\u1eddi d\u00f9ng ch\u1ec9 c\u00f3 th\u1ec3 truy c\u1eadp d\u1eef li\u1ec7u m\u00e0 h\u1ecd c\u00f3 quy\u1ec1n. S\u1eed d\u1ee5ng c\u00e1c ph\u01b0\u01a1ng ph\u00e1p nh\u01b0 ph\u00e2n quy\u1ec1n v\u00e0 ki\u1ec3m tra tr\u1ea1ng th\u00e1i phi\u00ean l\u00e0m vi\u1ec7c.<\/span><\/li>\n<\/ul>\n<\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>B\u1ea3o m\u1eadt m\u1ea1ng<\/b><span style=\"font-weight: 400;\">:<\/span>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">S\u1eed d\u1ee5ng HTTPS \u0111\u1ec3 m\u00e3 h\u00f3a d\u1eef li\u1ec7u khi truy\u1ec1n t\u1ea3i qua m\u1ea1ng. \u0110i\u1ec1u n\u00e0y gi\u00fap b\u1ea3o v\u1ec7 d\u1eef li\u1ec7u kh\u1ecfi vi\u1ec7c b\u1ecb ch\u1eb7n v\u00e0 nghe l\u00e9n trong qu\u00e1 tr\u00ecnh truy\u1ec1n t\u1ea3i.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">Ki\u1ec3m tra ch\u1ee9ng ch\u1ec9 SSL \u0111\u1ec3 \u0111\u1ea3m b\u1ea3o r\u1eb1ng server m\u00e0 \u1ee9ng d\u1ee5ng k\u1ebft n\u1ed1i l\u00e0 h\u1ee3p l\u1ec7 v\u00e0 an to\u00e0n.<\/span><\/li>\n<\/ul>\n<\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>Ch\u1ed1ng t\u1ea5n c\u00f4ng XSS v\u00e0 SQL Injection<\/b><span style=\"font-weight: 400;\">:<\/span>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">Ki\u1ec3m so\u00e1t v\u00e0 x\u00e1c th\u1ef1c d\u1eef li\u1ec7u \u0111\u1ea7u v\u00e0o t\u1eeb ng\u01b0\u1eddi d\u00f9ng \u0111\u1ec3 ng\u0103n ch\u1eb7n c\u00e1c t\u1ea5n c\u00f4ng nh\u01b0 XSS (Cross-Site Scripting) v\u00e0 SQL Injection. S\u1eed d\u1ee5ng c\u00e1c bi\u1ec7n ph\u00e1p nh\u01b0 escaping v\u00e0 prepared statements \u0111\u1ec3 b\u1ea3o v\u1ec7 \u1ee9ng d\u1ee5ng.<\/span><\/li>\n<\/ul>\n<\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>C\u1eadp nh\u1eadt v\u00e0 v\u00e1 l\u1ed7i th\u01b0\u1eddng xuy\u00ean<\/b><span style=\"font-weight: 400;\">:<\/span>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">Theo d\u00f5i v\u00e0 c\u1eadp nh\u1eadt \u1ee9ng d\u1ee5ng th\u01b0\u1eddng xuy\u00ean \u0111\u1ec3 kh\u1eafc ph\u1ee5c c\u00e1c l\u1ed7 h\u1ed5ng b\u1ea3o m\u1eadt. \u0110\u1ea3m b\u1ea3o s\u1eed d\u1ee5ng c\u00e1c th\u01b0 vi\u1ec7n v\u00e0 SDK m\u1edbi nh\u1ea5t v\u1edbi c\u00e1c b\u1ea3n v\u00e1 b\u1ea3o m\u1eadt \u0111\u00e3 \u0111\u01b0\u1ee3c \u00e1p d\u1ee5ng.<\/span><\/li>\n<\/ul>\n<\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>Qu\u1ea3n l\u00fd th\u1eddi gian phi\u00ean<\/b><span style=\"font-weight: 400;\">:<\/span>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">Thi\u1ebft l\u1eadp th\u1eddi gian h\u1ebft h\u1ea1n cho phi\u00ean l\u00e0m vi\u1ec7c c\u1ee7a ng\u01b0\u1eddi d\u00f9ng, t\u1ef1 \u0111\u1ed9ng \u0111\u0103ng xu\u1ea5t n\u1ebfu kh\u00f4ng ho\u1ea1t \u0111\u1ed9ng trong m\u1ed9t kho\u1ea3ng th\u1eddi gian nh\u1ea5t \u0111\u1ecbnh.<\/span><\/li>\n<\/ul>\n<\/li>\n<\/ol>\n<h3><strong>NSUserDefaults l\u00e0 g\u00ec? Khi n\u00e0o n\u00ean s\u1eed d\u1ee5ng n\u00f3 v\u00e0 khi n\u00e0o kh\u00f4ng?<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">NSUserDefaults<\/span><span style=\"font-weight: 400;\"> l\u00e0 m\u1ed9t l\u1edbp trong iOS cho ph\u00e9p l\u01b0u tr\u1eef v\u00e0 qu\u1ea3n l\u00fd c\u00e1c th\u00f4ng tin c\u1ea5u h\u00ecnh ho\u1eb7c d\u1eef li\u1ec7u nh\u1ecf m\u00e0 \u1ee9ng d\u1ee5ng c\u1ea7n. N\u00f3 cung c\u1ea5p m\u1ed9t c\u00e1ch \u0111\u01a1n gi\u1ea3n \u0111\u1ec3 l\u01b0u tr\u1eef c\u00e1c gi\u00e1 tr\u1ecb d\u1ea1ng key-value, bao g\u1ed3m c\u00e1c ki\u1ec3u d\u1eef li\u1ec7u nh\u01b0 <\/span><span style=\"font-weight: 400;\">String<\/span><span style=\"font-weight: 400;\">, <\/span><span style=\"font-weight: 400;\">Int<\/span><span style=\"font-weight: 400;\">, <\/span><span style=\"font-weight: 400;\">Bool<\/span><span style=\"font-weight: 400;\">, <\/span><span style=\"font-weight: 400;\">Array<\/span><span style=\"font-weight: 400;\">, v\u00e0 <\/span><span style=\"font-weight: 400;\">Dictionary<\/span><span style=\"font-weight: 400;\">. D\u1eef li\u1ec7u l\u01b0u tr\u1eef trong <\/span><span style=\"font-weight: 400;\">NSUserDefaults<\/span><span style=\"font-weight: 400;\"> s\u1ebd \u0111\u01b0\u1ee3c duy tr\u00ec gi\u1eefa c\u00e1c l\u1ea7n kh\u1edfi \u0111\u1ed9ng \u1ee9ng d\u1ee5ng.<\/span><\/p>\n<p><b>Khi n\u00e0o n\u00ean s\u1eed d\u1ee5ng NSUserDefaults?<\/b><\/p>\n<ol>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>L\u01b0u tr\u1eef c\u1ea5u h\u00ecnh ng\u01b0\u1eddi d\u00f9ng<\/b><span style=\"font-weight: 400;\">:<\/span>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">Khi b\u1ea1n c\u1ea7n l\u01b0u tr\u1eef c\u00e1c t\u00f9y ch\u1ecdn ho\u1eb7c thi\u1ebft l\u1eadp c\u1ee7a ng\u01b0\u1eddi d\u00f9ng nh\u01b0 ch\u1ebf \u0111\u1ed9 s\u00e1ng\/t\u1ed1i, ng\u00f4n ng\u1eef, ho\u1eb7c c\u00e1c th\u00f4ng s\u1ed1 c\u1ea5u h\u00ecnh kh\u00e1c m\u00e0 kh\u00f4ng c\u1ea7n l\u01b0u tr\u1eef ch\u00fang trong c\u01a1 s\u1edf d\u1eef li\u1ec7u.<\/span><\/li>\n<\/ul>\n<\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>D\u1eef li\u1ec7u nh\u1ecf v\u00e0 kh\u00f4ng nh\u1ea1y c\u1ea3m<\/b><span style=\"font-weight: 400;\">:<\/span>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">Khi b\u1ea1n c\u1ea7n l\u01b0u tr\u1eef m\u1ed9t l\u01b0\u1ee3ng d\u1eef li\u1ec7u nh\u1ecf (v\u00ed d\u1ee5 nh\u01b0 tr\u1ea1ng th\u00e1i UI, l\u1ea7n cu\u1ed1i c\u00f9ng ng\u01b0\u1eddi d\u00f9ng truy c\u1eadp m\u1ed9t m\u00e0n h\u00ecnh c\u1ee5 th\u1ec3) m\u00e0 kh\u00f4ng c\u1ea7n \u0111\u1ebfn hi\u1ec7u su\u1ea5t cao.<\/span><\/li>\n<\/ul>\n<\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>Th\u00f4ng tin c\u1ea7n truy c\u1eadp nhanh<\/b><span style=\"font-weight: 400;\">:<\/span>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">Khi b\u1ea1n c\u1ea7n truy c\u1eadp d\u1eef li\u1ec7u m\u1ed9t c\u00e1ch nhanh ch\u00f3ng m\u00e0 kh\u00f4ng c\u1ea7n ph\u1ea3i kh\u1edfi t\u1ea1o m\u1ed9t c\u01a1 s\u1edf d\u1eef li\u1ec7u ho\u1eb7c m\u1ed9t file l\u1edbn.<\/span><\/li>\n<\/ul>\n<\/li>\n<\/ol>\n<p><b>Khi n\u00e0o kh\u00f4ng n\u00ean s\u1eed d\u1ee5ng NSUserDefaults?<\/b><\/p>\n<ol>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>D\u1eef li\u1ec7u l\u1edbn ho\u1eb7c ph\u1ee9c t\u1ea1p<\/b><span style=\"font-weight: 400;\">:<\/span>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">Kh\u00f4ng n\u00ean s\u1eed d\u1ee5ng <\/span><span style=\"font-weight: 400;\">NSUserDefaults<\/span><span style=\"font-weight: 400;\"> \u0111\u1ec3 l\u01b0u tr\u1eef c\u00e1c \u0111\u1ed1i t\u01b0\u1ee3ng l\u1edbn ho\u1eb7c ph\u1ee9c t\u1ea1p, nh\u01b0 h\u00ecnh \u1ea3nh ho\u1eb7c video, v\u00ec \u0111i\u1ec1u n\u00e0y c\u00f3 th\u1ec3 l\u00e0m ch\u1eadm \u1ee9ng d\u1ee5ng v\u00e0 g\u00e2y ra c\u00e1c v\u1ea5n \u0111\u1ec1 v\u1ec1 hi\u1ec7u su\u1ea5t.<\/span><\/li>\n<\/ul>\n<\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>D\u1eef li\u1ec7u nh\u1ea1y c\u1ea3m<\/b><span style=\"font-weight: 400;\">:<\/span>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">Kh\u00f4ng l\u01b0u tr\u1eef th\u00f4ng tin nh\u1ea1y c\u1ea3m nh\u01b0 m\u1eadt kh\u1ea9u, th\u00f4ng tin th\u1ebb t\u00edn d\u1ee5ng ho\u1eb7c b\u1ea5t k\u1ef3 d\u1eef li\u1ec7u c\u00e1 nh\u00e2n n\u00e0o trong <\/span><span style=\"font-weight: 400;\">NSUserDefaults<\/span><span style=\"font-weight: 400;\">. Thay v\u00e0o \u0111\u00f3, n\u00ean s\u1eed d\u1ee5ng Keychain \u0111\u1ec3 b\u1ea3o m\u1eadt th\u00f4ng tin nh\u1ea1y c\u1ea3m.<\/span><\/li>\n<\/ul>\n<\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>Th\u00f4ng tin c\u1ea7n \u0111\u01b0\u1ee3c t\u1ed5 ch\u1ee9c t\u1ed1t<\/b><span style=\"font-weight: 400;\">:<\/span>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">N\u1ebfu b\u1ea1n c\u1ea7n l\u01b0u tr\u1eef m\u1ed9t c\u1ea5u tr\u00fac d\u1eef li\u1ec7u ph\u1ee9c t\u1ea1p ho\u1eb7c c\u00f3 m\u1ed1i quan h\u1ec7 gi\u1eefa c\u00e1c \u0111\u1ed1i t\u01b0\u1ee3ng, th\u00ec s\u1eed d\u1ee5ng Core Data ho\u1eb7c m\u1ed9t c\u01a1 s\u1edf d\u1eef li\u1ec7u kh\u00e1c s\u1ebd h\u1ee3p l\u00fd h\u01a1n.<\/span><\/li>\n<\/ul>\n<\/li>\n<\/ol>\n<h3><strong>S\u1ef1 kh\u00e1c nhau gi\u1eefa KVO (Key-Value Observing) v\u00e0 NotificationCenter l\u00e0 g\u00ec?<\/strong><\/h3>\n<table>\n<tbody>\n<tr>\n<td><b>Ti\u00eau ch\u00ed\u00a0<\/b><\/td>\n<td><b>KVO (Key-Value Observing)<\/b><\/td>\n<td><b>NotificationCenter<\/b><\/td>\n<\/tr>\n<tr>\n<td><b>\u0110\u1ecbnh ngh\u0129a\u00a0<\/b><\/td>\n<td><span style=\"font-weight: 400;\">C\u01a1 ch\u1ebf cho ph\u00e9p theo d\u00f5i s\u1ef1 thay \u0111\u1ed5i c\u1ee7a thu\u1ed9c t\u00ednh<\/span><\/td>\n<td><span style=\"font-weight: 400;\">C\u01a1 ch\u1ebf cho ph\u00e9p g\u1eedi v\u00e0 nh\u1eadn th\u00f4ng b\u00e1o gi\u1eefa c\u00e1c \u0111\u1ed1i t\u01b0\u1ee3ng<\/span><\/td>\n<\/tr>\n<tr>\n<td><b>C\u00e1ch ho\u1ea1t \u0111\u1ed9ng\u00a0<\/b><\/td>\n<td><span style=\"font-weight: 400;\">\u0110\u0103ng k\u00fd \u0111\u1ec3 theo d\u00f5i thu\u1ed9c t\u00ednh c\u1ee5 th\u1ec3<\/span><\/td>\n<td><span style=\"font-weight: 400;\">\u0110\u0103ng k\u00fd \u0111\u1ec3 nh\u1eadn th\u00f4ng b\u00e1o t\u1eeb NotificationCenter<\/span><\/td>\n<\/tr>\n<tr>\n<td><b>S\u1eed d\u1ee5ng\u00a0<\/b><\/td>\n<td><span style=\"font-weight: 400;\">Theo d\u00f5i s\u1ef1 thay \u0111\u1ed5i c\u1ee7a thu\u1ed9c t\u00ednh<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Th\u00f4ng b\u00e1o v\u1ec1 s\u1ef1 ki\u1ec7n m\u00e0 nhi\u1ec1u \u0111\u1ed1i t\u01b0\u1ee3ng c\u00f3 th\u1ec3 quan t\u00e2m<\/span><\/td>\n<\/tr>\n<tr>\n<td><b>\u01afu \u0111i\u1ec3m<\/b><\/td>\n<td><span style=\"font-weight: 400;\">&#8211; Th\u00f4ng b\u00e1o t\u1ee9c th\u1eddi khi c\u00f3 s\u1ef1 thay \u0111\u1ed5i<\/span><\/p>\n<p><span style=\"font-weight: 400;\">&#8211; Gi\u00fap \u0111\u1ed3ng b\u1ed9 h\u00f3a d\u1eef li\u1ec7u<\/span><\/td>\n<td><span style=\"font-weight: 400;\">&#8211; Linh ho\u1ea1t h\u01a1n trong vi\u1ec7c g\u1eedi v\u00e0 nh\u1eadn th\u00f4ng b\u00e1o<\/span><\/p>\n<p><span style=\"font-weight: 400;\">&#8211; C\u00f3 th\u1ec3 g\u1eedi th\u00f4ng b\u00e1o \u0111\u1ebfn nhi\u1ec1u \u0111\u1ed1i t\u01b0\u1ee3ng<\/span><\/td>\n<\/tr>\n<tr>\n<td><b>Nh\u01b0\u1ee3c \u0111i\u1ec3m\u00a0<\/b><\/td>\n<td><span style=\"font-weight: 400;\">&#8211; C\u1ea7n qu\u1ea3n l\u00fd \u0111\u0103ng k\u00fd v\u00e0 h\u1ee7y \u0111\u0103ng k\u00fd ch\u00ednh x\u00e1c<\/span><\/p>\n<p><span style=\"font-weight: 400;\">&#8211; Ch\u1ec9 theo d\u00f5i thu\u1ed9c t\u00ednh c\u1ee5 th\u1ec3<\/span><\/td>\n<td><span style=\"font-weight: 400;\">&#8211; C\u00f3 th\u1ec3 kh\u00f3 qu\u1ea3n l\u00fd nhi\u1ec1u observer v\u00e0 th\u00f4ng b\u00e1o<\/span><\/p>\n<p><span style=\"font-weight: 400;\">&#8211; Kh\u00f4ng t\u1ef1 \u0111\u1ed9ng d\u1ecdn d\u1eb9p observer<\/span><\/td>\n<\/tr>\n<tr>\n<td><b>T\u00ecnh hu\u1ed1ng s\u1eed d\u1ee5ng<\/b><\/td>\n<td><span style=\"font-weight: 400;\">Khi c\u1ea7n \u0111\u1ed3ng b\u1ed9 h\u00f3a giao di\u1ec7n ng\u01b0\u1eddi d\u00f9ng v\u1edbi d\u1eef li\u1ec7u<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Khi c\u1ea7n th\u00f4ng b\u00e1o v\u1ec1 s\u1ef1 ki\u1ec7n chung m\u00e0 kh\u00f4ng c\u1ea7n bi\u1ebft \u0111\u1ed1i t\u01b0\u1ee3ng nh\u1eadn<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h3><strong>L\u00e0m th\u1ebf n\u00e0o \u0111\u1ec3 tri\u1ec3n khai c\u00e1c y\u00eau c\u1ea7u m\u1ea1ng c\u00f3 th\u1eddi gian d\u00e0i v\u1edbi URLSession v\u00e0 t\u00e1c v\u1ee5 n\u1ec1n (background task)?<\/strong><\/h3>\n<p><b>T\u1ea1o m\u1ed9t <\/b><b>URLSessionConfiguration<\/b><b> v\u1edbi Background Configuration<\/b><\/p>\n<p><span style=\"font-weight: 400;\">Tr\u01b0\u1edbc ti\u00ean, b\u1ea1n c\u1ea7n t\u1ea1o m\u1ed9t phi\u00ean <\/span><span style=\"font-weight: 400;\">URLSession<\/span><span style=\"font-weight: 400;\"> v\u1edbi c\u1ea5u h\u00ecnh background. \u0110i\u1ec1u n\u00e0y cho ph\u00e9p y\u00eau c\u1ea7u m\u1ea1ng ti\u1ebfp t\u1ee5c th\u1ef1c hi\u1ec7n ngay c\u1ea3 khi \u1ee9ng d\u1ee5ng kh\u00f4ng ho\u1ea1t \u0111\u1ed9ng.<\/span><\/p>\n<pre><span style=\"font-weight: 400;\">let config = URLSessionConfiguration.background(withIdentifier: \"com.example.app.background\")<\/span>\r\n\r\n<span style=\"font-weight: 400;\">let session = URLSession(configuration: config, delegate: self, delegateQueue: nil)<\/span><\/pre>\n<p><b>Th\u1ef1c hi\u1ec7n y\u00eau c\u1ea7u m\u1ea1ng<\/b><\/p>\n<p><span style=\"font-weight: 400;\">S\u1eed d\u1ee5ng <\/span><span style=\"font-weight: 400;\">URLSession<\/span><span style=\"font-weight: 400;\"> \u0111\u1ec3 th\u1ef1c hi\u1ec7n y\u00eau c\u1ea7u m\u1ea1ng. B\u1ea1n c\u00f3 th\u1ec3 s\u1eed d\u1ee5ng c\u00e1c ph\u01b0\u01a1ng th\u1ee9c nh\u01b0 <\/span><span style=\"font-weight: 400;\">dataTask(with:completionHandler:)<\/span><span style=\"font-weight: 400;\"> ho\u1eb7c <\/span><span style=\"font-weight: 400;\">uploadTask(with:from:)<\/span><span style=\"font-weight: 400;\"> t\u00f9y thu\u1ed9c v\u00e0o y\u00eau c\u1ea7u c\u1ee7a b\u1ea1n.<\/span><\/p>\n<pre><span style=\"font-weight: 400;\">let url = URL(string: \"https:\/\/example.com\/large-file\")!<\/span>\r\n\r\n<span style=\"font-weight: 400;\">let task = session.downloadTask(with: url)<\/span>\r\n\r\n<span style=\"font-weight: 400;\">task.resume()<\/span><\/pre>\n<p><b>X\u1eed l\u00fd k\u1ebft qu\u1ea3 trong Delegate<\/b><\/p>\n<p><span style=\"font-weight: 400;\">C\u1ea7n \u0111\u1ea3m b\u1ea3o r\u1eb1ng b\u1ea1n tu\u00e2n theo giao th\u1ee9c <\/span><span style=\"font-weight: 400;\">URLSessionDelegate<\/span><span style=\"font-weight: 400;\">, <\/span><span style=\"font-weight: 400;\">URLSessionTaskDelegate<\/span><span style=\"font-weight: 400;\">, ho\u1eb7c <\/span><span style=\"font-weight: 400;\">URLSessionDownloadDelegate<\/span><span style=\"font-weight: 400;\"> \u0111\u1ec3 nh\u1eadn th\u00f4ng b\u00e1o v\u1ec1 ti\u1ebfn tr\u00ecnh t\u1ea3i xu\u1ed1ng ho\u1eb7c ho\u00e0n t\u1ea5t. D\u01b0\u1edbi \u0111\u00e2y l\u00e0 m\u1ed9t v\u00ed d\u1ee5 v\u1ec1 c\u00e1ch x\u1eed l\u00fd ho\u00e0n t\u1ea5t t\u1ea3i xu\u1ed1ng.<\/span><\/p>\n<pre><span style=\"font-weight: 400;\">extension YourClass: URLSessionDownloadDelegate {<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask, didFinishDownloadingTo location: URL) {<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\/\/ X\u1eed l\u00fd file t\u1ea3i v\u1ec1<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0}<\/span>\r\n\r\n<span style=\"font-weight: 400;\">\u00a0\u00a0\u00a0\u00a0func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask, didWriteData bytesWritten: Int64, totalBytesWritten: Int64, totalBytesExpectedToWrite: Int64) {<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0let progress = Double(totalBytesWritten) \/ Double(totalBytesExpectedToWrite)<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0print(\"Ti\u1ebfn tr\u00ecnh t\u1ea3i xu\u1ed1ng: \\(progress * 100)%\")<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0}<\/span>\r\n<span style=\"font-weight: 400;\">}<\/span><\/pre>\n<p><b>X\u1eed l\u00fd Background Task<\/b><\/p>\n<p><span style=\"font-weight: 400;\">Khi \u1ee9ng d\u1ee5ng chuy\u1ec3n sang n\u1ec1n, b\u1ea1n c\u00f3 th\u1ec3 c\u1ea7n y\u00eau c\u1ea7u th\u00eam th\u1eddi gian \u0111\u1ec3 ho\u00e0n th\u00e0nh y\u00eau c\u1ea7u m\u1ea1ng. \u0110\u1ec3 l\u00e0m \u0111i\u1ec1u n\u00e0y, b\u1ea1n c\u00f3 th\u1ec3 s\u1eed d\u1ee5ng <\/span><span style=\"font-weight: 400;\">beginBackgroundTask(withName:expirationHandler:)<\/span><span style=\"font-weight: 400;\">.<\/span><\/p>\n<pre><span style=\"font-weight: 400;\">var backgroundTask: UIBackgroundTaskIdentifier = .invalid<\/span>\r\n<span style=\"font-weight: 400;\">\r\nbackgroundTask = UIApplication.shared.beginBackgroundTask(withName: \"NetworkRequest\") {<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\/\/ X\u1eed l\u00fd khi background task h\u1ebft th\u1eddi gian<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0UIApplication.shared.endBackgroundTask(backgroundTask)<\/span>\r\n<span style=\"font-weight: 400;\">}<\/span>\r\n\r\n<span style=\"font-weight: 400;\">let task = session.dataTask(with: url) { (data, response, error) in<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0\/\/ X\u1eed l\u00fd y\u00eau c\u1ea7u m\u1ea1ng<\/span>\r\n<span style=\"font-weight: 400;\"> \u00a0\u00a0\u00a0UIApplication.shared.endBackgroundTask(backgroundTask)<\/span>\r\n<span style=\"font-weight: 400;\">}<\/span>\r\n<span style=\"font-weight: 400;\">task.resume()<\/span><\/pre>\n<p><b>X\u1eed l\u00fd K\u1ebft th\u00fac Background Task<\/b><\/p>\n<p><span style=\"font-weight: 400;\">Khi y\u00eau c\u1ea7u m\u1ea1ng ho\u00e0n t\u1ea5t, h\u00e3y \u0111\u1ea3m b\u1ea3o g\u1ecdi <\/span><span style=\"font-weight: 400;\">endBackgroundTask(_:)<\/span><span style=\"font-weight: 400;\"> \u0111\u1ec3 k\u1ebft th\u00fac background task v\u00e0 gi\u1ea3i ph\u00f3ng t\u00e0i nguy\u00ean.<\/span><\/p>\n<p><b>Ki\u1ec3m tra tr\u1ea1ng th\u00e1i t\u1ea3i xu\u1ed1ng<\/b><\/p>\n<p><span style=\"font-weight: 400;\">B\u1ea1n c\u00f3 th\u1ec3 theo d\u00f5i tr\u1ea1ng th\u00e1i t\u1ea3i xu\u1ed1ng b\u1eb1ng c\u00e1ch ki\u1ec3m tra th\u00f4ng b\u00e1o t\u1eeb delegate ho\u1eb7c l\u01b0u tr\u1eef tr\u1ea1ng th\u00e1i trong <\/span><span style=\"font-weight: 400;\">UserDefaults<\/span><span style=\"font-weight: 400;\"> ho\u1eb7c m\u1ed9t h\u1ec7 th\u1ed1ng l\u01b0u tr\u1eef kh\u00e1c \u0111\u1ec3 c\u1eadp nh\u1eadt cho ng\u01b0\u1eddi d\u00f9ng.<\/span><\/p>\n<h3><strong>L\u00e0m th\u1ebf n\u00e0o \u0111\u1ec3 h\u1ea1n ch\u1ebf \u0111\u1ebfn m\u1ee9c th\u1ea5p nh\u1ea5t hi\u1ec7n t\u01b0\u1ee3ng b\u1ecb Crash (hay t\u1eaft \u0111\u1ed9t ng\u1ed9t) c\u1ee7a \u1ee9ng d\u1ee5ng iOS?<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">\u0110\u1ec3 h\u1ea1n ch\u1ebf hi\u1ec7n t\u01b0\u1ee3ng crash (t\u1eaft \u0111\u1ed9t ng\u1ed9t) c\u1ee7a \u1ee9ng d\u1ee5ng iOS, b\u1ea1n c\u00f3 th\u1ec3 \u00e1p d\u1ee5ng c\u00e1c ph\u01b0\u01a1ng ph\u00e1p sau:<\/span><\/p>\n<p><b> X\u1eed l\u00fd l\u1ed7i t\u1ed1t<\/b><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>S\u1eed d\u1ee5ng <\/b><b>do-catch<\/b><span style=\"font-weight: 400;\">: \u0110\u1ea3m b\u1ea3o r\u1eb1ng b\u1ea1n s\u1eed d\u1ee5ng <\/span><span style=\"font-weight: 400;\">do-catch<\/span><span style=\"font-weight: 400;\"> \u0111\u1ec3 x\u1eed l\u00fd c\u00e1c l\u1ed7i khi th\u1ef1c hi\u1ec7n c\u00e1c t\u00e1c v\u1ee5 c\u00f3 th\u1ec3 g\u00e2y ra l\u1ed7i, ch\u1eb3ng h\u1ea1n nh\u01b0 \u0111\u1ecdc file ho\u1eb7c th\u1ef1c hi\u1ec7n y\u00eau c\u1ea7u m\u1ea1ng.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>Ki\u1ec3m tra optional<\/b><span style=\"font-weight: 400;\">: S\u1eed d\u1ee5ng <\/span><span style=\"font-weight: 400;\">if let<\/span><span style=\"font-weight: 400;\"> ho\u1eb7c <\/span><span style=\"font-weight: 400;\">guard let<\/span><span style=\"font-weight: 400;\"> \u0111\u1ec3 ki\u1ec3m tra c\u00e1c gi\u00e1 tr\u1ecb optional tr\u01b0\u1edbc khi s\u1eed d\u1ee5ng ch\u00fang, gi\u00fap tr\u00e1nh l\u1ed7i khi truy c\u1eadp v\u00e0o gi\u00e1 tr\u1ecb nil.<\/span><\/li>\n<\/ul>\n<p><b> Gi\u00e1m s\u00e1t v\u00e0 ghi log<\/b><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>S\u1eed d\u1ee5ng c\u00f4ng c\u1ee5 gi\u00e1m s\u00e1t<\/b><span style=\"font-weight: 400;\">: S\u1eed d\u1ee5ng c\u00e1c c\u00f4ng c\u1ee5 nh\u01b0 Firebase Crashlytics ho\u1eb7c Sentry \u0111\u1ec3 theo d\u00f5i v\u00e0 ghi l\u1ea1i th\u00f4ng tin v\u1ec1 crash. \u0110i\u1ec1u n\u00e0y gi\u00fap b\u1ea1n n\u1eafm b\u1eaft \u0111\u01b0\u1ee3c c\u00e1c nguy\u00ean nh\u00e2n g\u00e2y ra l\u1ed7i v\u00e0 kh\u1eafc ph\u1ee5c ch\u00fang k\u1ecbp th\u1eddi.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>Ghi log<\/b><span style=\"font-weight: 400;\">: Ghi l\u1ea1i c\u00e1c s\u1ef1 ki\u1ec7n quan tr\u1ecdng v\u00e0 l\u1ed7i trong \u1ee9ng d\u1ee5ng \u0111\u1ec3 gi\u00fap b\u1ea1n ph\u00e2n t\u00edch nguy\u00ean nh\u00e2n crash khi c\u00f3 v\u1ea5n \u0111\u1ec1 x\u1ea3y ra.<\/span><\/li>\n<\/ul>\n<p><b> T\u1ed1i \u01b0u h\u00f3a hi\u1ec7u su\u1ea5t<\/b><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>Qu\u1ea3n l\u00fd b\u1ed9 nh\u1edb<\/b><span style=\"font-weight: 400;\">: Tr\u00e1nh r\u00f2 r\u1ec9 b\u1ed9 nh\u1edb b\u1eb1ng c\u00e1ch s\u1eed d\u1ee5ng <\/span><span style=\"font-weight: 400;\">weak<\/span><span style=\"font-weight: 400;\"> v\u00e0 <\/span><span style=\"font-weight: 400;\">unowned<\/span><span style=\"font-weight: 400;\"> cho c\u00e1c tham chi\u1ebfu v\u00f2ng l\u1eb7p trong c\u00e1c closure v\u00e0 delegate.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>Ki\u1ec3m tra hi\u1ec7u su\u1ea5t<\/b><span style=\"font-weight: 400;\">: S\u1eed d\u1ee5ng Instruments \u0111\u1ec3 ph\u00e2n t\u00edch hi\u1ec7u su\u1ea5t c\u1ee7a \u1ee9ng d\u1ee5ng v\u00e0 ph\u00e1t hi\u1ec7n c\u00e1c v\u1ea5n \u0111\u1ec1 c\u00f3 th\u1ec3 d\u1eabn \u0111\u1ebfn crash, ch\u1eb3ng h\u1ea1n nh\u01b0 vi\u1ec7c s\u1eed d\u1ee5ng qu\u00e1 nhi\u1ec1u b\u1ed9 nh\u1edb.<\/span><\/li>\n<\/ul>\n<p><b> Ki\u1ec3m tra \u0111\u1ea7u v\u00e0o<\/b><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>Ki\u1ec3m tra d\u1eef li\u1ec7u \u0111\u1ea7u v\u00e0o<\/b><span style=\"font-weight: 400;\">: \u0110\u1ea3m b\u1ea3o r\u1eb1ng d\u1eef li\u1ec7u \u0111\u1ea7u v\u00e0o (v\u00ed d\u1ee5: t\u1eeb ng\u01b0\u1eddi d\u00f9ng ho\u1eb7c t\u1eeb API) l\u00e0 h\u1ee3p l\u1ec7 tr\u01b0\u1edbc khi s\u1eed d\u1ee5ng ch\u00fang trong \u1ee9ng d\u1ee5ng.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>X\u1eed l\u00fd d\u1eef li\u1ec7u b\u1ea5t h\u1ee3p l\u1ec7<\/b><span style=\"font-weight: 400;\">: Cung c\u1ea5p c\u00e1c th\u00f4ng b\u00e1o l\u1ed7i r\u00f5 r\u00e0ng v\u00e0 h\u1ee3p l\u00fd cho ng\u01b0\u1eddi d\u00f9ng khi c\u00f3 d\u1eef li\u1ec7u kh\u00f4ng h\u1ee3p l\u1ec7.<\/span><\/li>\n<\/ul>\n<p><b> Th\u1ef1c hi\u1ec7n test<\/b><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>Ki\u1ec3m tra t\u1ef1 \u0111\u1ed9ng<\/b><span style=\"font-weight: 400;\">: Vi\u1ebft c\u00e1c b\u00e0i ki\u1ec3m tra t\u1ef1 \u0111\u1ed9ng (unit tests v\u00e0 UI tests) \u0111\u1ec3 ki\u1ec3m tra c\u00e1c ch\u1ee9c n\u0103ng c\u1ee7a \u1ee9ng d\u1ee5ng. \u0110i\u1ec1u n\u00e0y gi\u00fap ph\u00e1t hi\u1ec7n l\u1ed7i trong giai \u0111o\u1ea1n ph\u00e1t tri\u1ec3n.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>Ki\u1ec3m tra tr\u00ean c\u00e1c thi\u1ebft b\u1ecb kh\u00e1c nhau<\/b><span style=\"font-weight: 400;\">: Th\u1ef1c hi\u1ec7n ki\u1ec3m tra tr\u00ean nhi\u1ec1u lo\u1ea1i thi\u1ebft b\u1ecb v\u00e0 phi\u00ean b\u1ea3n iOS kh\u00e1c nhau \u0111\u1ec3 \u0111\u1ea3m b\u1ea3o r\u1eb1ng \u1ee9ng d\u1ee5ng ho\u1ea1t \u0111\u1ed9ng \u1ed5n \u0111\u1ecbnh tr\u00ean t\u1ea5t c\u1ea3 c\u00e1c m\u00f4i tr\u01b0\u1eddng.<\/span><\/li>\n<\/ul>\n<p><b> Qu\u1ea3n l\u00fd background tasks<\/b><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>K\u1ebft th\u00fac c\u00e1c task kh\u00f4ng c\u1ea7n thi\u1ebft<\/b><span style=\"font-weight: 400;\">: \u0110\u1ea3m b\u1ea3o r\u1eb1ng b\u1ea1n qu\u1ea3n l\u00fd c\u00e1c background tasks m\u1ed9t c\u00e1ch hi\u1ec7u qu\u1ea3 v\u00e0 k\u1ebft th\u00fac ch\u00fang khi kh\u00f4ng c\u00f2n c\u1ea7n thi\u1ebft.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>S\u1eed d\u1ee5ng \u0111\u00fang APIs<\/b><span style=\"font-weight: 400;\">: \u0110\u1ed1i v\u1edbi c\u00e1c t\u00e1c v\u1ee5 m\u1ea1ng d\u00e0i, h\u00e3y s\u1eed d\u1ee5ng <\/span><span style=\"font-weight: 400;\">URLSession<\/span><span style=\"font-weight: 400;\"> v\u1edbi background configuration \u0111\u1ec3 \u0111\u1ea3m b\u1ea3o r\u1eb1ng ch\u00fang c\u00f3 th\u1ec3 ti\u1ebfp t\u1ee5c ch\u1ea1y ngay c\u1ea3 khi \u1ee9ng d\u1ee5ng kh\u00f4ng ho\u1ea1t \u0111\u1ed9ng.<\/span><\/li>\n<\/ul>\n<p><b> C\u1eadp nh\u1eadt th\u01b0 vi\u1ec7n v\u00e0 c\u00f4ng ngh\u1ec7<\/b><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>C\u1eadp nh\u1eadt th\u01b0\u1eddng xuy\u00ean<\/b><span style=\"font-weight: 400;\">: \u0110\u1ea3m b\u1ea3o r\u1eb1ng b\u1ea1n s\u1eed d\u1ee5ng c\u00e1c phi\u00ean b\u1ea3n m\u1edbi nh\u1ea5t c\u1ee7a c\u00e1c th\u01b0 vi\u1ec7n v\u00e0 framework \u0111\u1ec3 t\u1eadn d\u1ee5ng c\u00e1c b\u1ea3n s\u1eeda l\u1ed7i v\u00e0 c\u1ea3i ti\u1ebfn hi\u1ec7u su\u1ea5t.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>Theo d\u00f5i c\u00e1c thay \u0111\u1ed5i trong iOS<\/b><span style=\"font-weight: 400;\">: Lu\u00f4n c\u1eadp nh\u1eadt ki\u1ebfn th\u1ee9c v\u1ec1 c\u00e1c thay \u0111\u1ed5i trong API v\u00e0 c\u00f4ng ngh\u1ec7 m\u1edbi \u0111\u1ec3 \u0111\u1ea3m b\u1ea3o \u1ee9ng d\u1ee5ng c\u1ee7a b\u1ea1n t\u01b0\u01a1ng th\u00edch v\u00e0 ho\u1ea1t \u0111\u1ed9ng \u1ed5n \u0111\u1ecbnh.<\/span><\/li>\n<\/ul>\n<h2><span class=\"ez-toc-section\" id=\"Tong_ket_cau_hoi_phong_van_iOS_Developer\"><\/span><strong>T\u1ed5ng k\u1ebft c\u00e2u h\u1ecfi ph\u1ecfng v\u1ea5n iOS Developer<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p><span style=\"font-weight: 400;\">Vi\u1ec7c chu\u1ea9n b\u1ecb cho c\u00e1c cu\u1ed9c ph\u1ecfng v\u1ea5n l\u00e0 \u0111i\u1ec1u c\u1ea7n thi\u1ebft \u0111\u1ec3 \u0111\u1ea1t \u0111\u01b0\u1ee3c th\u00e0nh c\u00f4ng. B\u00e0i vi\u1ebft n\u00e0y \u0111\u00e3 tr\u00ecnh b\u00e0y m\u1ed9t lo\u1ea1t c\u00e2u h\u1ecfi ph\u1ecfng v\u1ea5n iOS Developer ph\u1ed5 bi\u1ebfn li\u00ean quan \u0111\u1ebfn Swift, UIKit, SwiftUI v\u00e0 c\u00e1c c\u00f4ng ngh\u1ec7 kh\u00e1c, c\u00f9ng v\u1edbi nh\u1eefng c\u00e2u tr\u1ea3 l\u1eddi ng\u1eafn g\u1ecdn nh\u01b0ng \u0111\u1ea7y \u0111\u1ee7 \u00fd. Qua \u0111\u00f3, b\u1ea1n kh\u00f4ng ch\u1ec9 n\u1eafm v\u1eefng c\u00e1c kh\u00e1i ni\u1ec7m v\u00e0 k\u1ef9 thu\u1eadt quan tr\u1ecdng m\u00e0 c\u00f2n c\u00f3 c\u01a1 h\u1ed9i r\u00e8n luy\u1ec7n kh\u1ea3 n\u0103ng gi\u1ea3i th\u00edch v\u00e0 tr\u00ecnh b\u00e0y ki\u1ebfn th\u1ee9c c\u1ee7a m\u00ecnh.<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"<p>iOS Developer l\u00e0 chuy\u00ean gia t\u1ea1o \u1ee9ng d\u1ee5ng cho h\u1ec7 \u0111i\u1ec1u h\u00e0nh iOS c\u1ee7a Apple. Nh\u1eefng nh\u00e0 ph\u00e1t tri\u1ec3n n\u00e0y c\u00f3 hi\u1ec3u bi\u1ebft s\u00e2u s\u1eafc v\u1ec1 h\u1ec7 sinh th\u00e1i iOS. B\u00e0i vi\u1ebft sau \u0111\u00e2y s\u1ebd t\u1ed5ng h\u1ee3p c\u00e1c c\u00e2u h\u1ecfi ph\u1ecfng v\u1ea5n iOS Developer ph\u1ed5 bi\u1ebfn, bao g\u1ed3m c\u00e1c ch\u1ee7 \u0111\u1ec1 v\u1ec1 framework, h\u01b0\u1edbng d\u1eabn [&hellip;]<\/p>\n","protected":false},"author":203,"featured_media":81607,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_gspb_post_css":"","footnotes":""},"categories":[109,99,94],"tags":[],"class_list":["post-81399","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-chuyen-mon-it","category-developer","category-su-nghiep-it"],"blocksy_meta":[],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v26.8 (Yoast SEO v27.7) - https:\/\/yoast.com\/product\/yoast-seo-premium-wordpress\/ -->\n<title>Top 40+ c\u00e2u h\u1ecfi ph\u1ecfng v\u1ea5n iOS Developer th\u01b0\u1eddng g\u1eb7p - ITviec Blog<\/title>\n<meta name=\"description\" content=\"B\u00e0i vi\u1ebft t\u1ed5ng h\u1ee3p c\u00e1c c\u00e2u h\u1ecfi ph\u1ecfng v\u1ea5n iOS Developer ph\u1ed5 bi\u1ebfn, bao g\u1ed3m c\u00e1c ch\u1ee7 \u0111\u1ec1 v\u1ec1 framework, h\u01b0\u1edbng d\u1eabn thi\u1ebft k\u1ebf v\u00e0 Swift, Objective-C.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/itviec.com\/blog\/cau-hoi-phong-van-ios-developer\/\" \/>\n<meta property=\"og:locale\" content=\"vi_VN\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Top 40+ c\u00e2u h\u1ecfi ph\u1ecfng v\u1ea5n iOS Developer th\u01b0\u1eddng g\u1eb7p\" \/>\n<meta property=\"og:description\" content=\"iOS Developer l\u00e0 chuy\u00ean gia t\u1ea1o \u1ee9ng d\u1ee5ng cho h\u1ec7 \u0111i\u1ec1u h\u00e0nh iOS c\u1ee7a Apple. 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