作者huangcooly (弱小豪)
看板MacDev
標題[問題] weak 屬性release時機
時間Tue Oct 3 17:38:07 2017
最近做了一些嘗試
遇到一個問題
我在ViewController中有兩個property為
@property (weak, nonatomic) UKTextField *myTextField;
@property (weak, nonatomic) Person *person;
UKTextField為繼承UITextField的類別
Person為自己定義的類別
兩個類別我都有覆寫dealloc的方法
讓兩個物件被回收時可以顯示Log
測試如下
- (void)viewDidLoad {
[super viewDidLoad];
NSLog(@"viewDidLoad Start");
//Assigning retained object to weak variable;
//object will be released after assignment
myTextField = [[UKTextField alloc] init];
//Assigning retained object to weak variable;
//object will be released after assignment
person = [Person new];
}
-(void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];
NSLog(@"viewWillAppear Start");
}
-(void)viewDidAppear:(BOOL)animated
{
[super viewDidAppear:animated];
NSLog(@"viewDidAppear Start");
}
Log內容出現順序如下
1.viewDidLoad Start
2.Person Dealloc
3.viewWillAppear Start
4.UKTextField dealloc
5.viewDidAppear Start
問題：
將UKTextField與Person皆設定為weak
就ARC來說當weak的物件應該再被指派完之後應該在viewDidLoad就會被回收了
但為什麼UKTextField會在viewWillAppear才會被回收呢??
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※ 編輯: huangcooly (42.77.201.168), 10/03/2017 17:44:59
1F：推 darktt: release是從class的變數開始，直到變數全部release完了， 10/03 19:06
2F：→ darktt: class本體才行release 10/03 19:06
3F：→ yuanruo: 用weak初始化對像，為了優化其實底層是調用class method 10/03 19:55
4F：→ yuanruo: 等同於你初始完後它會被加到一個autoreleasePool裡 10/03 19:56
5F：→ yuanruo: autoreleasePool 在viewDidload返回時，還沒drain 10/03 19:58
6F：→ yuanruo: 它被延遲到willAppear 到didAppear中某個方法被drain 10/03 19:59
7F：→ yuanruo: 詳細下斷點自己去追stackTree 關鍵字AutoreleasePoolPage 10/03 20:01
8F：→ yuanruo: 或是你可以把code編成C++ 直接看源碼 10/03 20:07