[問題] weak 屬性release時機

[huangcooly (弱小豪)]

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
推 darktt: release是從class的變數開始，直到變數全部release完了，
→ darktt: class本體才行release
→ yuanruo: 用weak初始化對像，為了優化其實底層是調用class method
→ yuanruo: 等同於你初始完後它會被加到一個autoreleasePool裡
→ yuanruo: autoreleasePool 在viewDidload返回時，還沒drain
→ yuanruo: 它被延遲到willAppear 到didAppear中某個方法被drain
→ yuanruo: 詳細下斷點自己去追stackTree 關鍵字AutoreleasePoolPage
→ yuanruo: 或是你可以把code編成C++ 直接看源碼