Objective-C：理解ARC

Question

我是Objective-C的新手。 以下是關於ARC的一些簡單代碼的理解（如在注釋中），用於以編程方式添加子視圖。 如果我錯了，請糾正我。 特別是在這個聲明上：

“ViewController弱點指向myView”ACTUALLY意味着_myView（ViewController的ivar）弱指向UIView對象

// _myView stores a pointer pointing to a UIView object
// "ViewController points to myView weakly" ACTUALLY means that _myView (ViewController's ivar) points to a UIView object weakly

@interface ViewController ()
@property (nonatomic,weak) UIView *myView;
@end

@implementation
@synthesize myView = _myView;
@end

- (void)viewDidLoad
{
    [superviewDidLoad];
    CGRect viewRect = CGRectMake(10, 10, 100, 100);

    // a UIView object is alloc/inited    
    // mv is a pointer pointing to the UIView object strongly (hence the owner of it)
    UIView *mv = [[UIView alloc] initWithFrame:viewRect];

   // _myView points to the UIView object weakly 
   // Now the UIView object now have two pointers pointing to it
   // mv points to it strongly
   // _myView points to it weakly, hence NOT a owner 
   self.myView = mv;

   // self.view points to the UIView object strongly
   // Now UIView object now have THREE pointer pointing to it
   // Two strong and one weak
   [self.view addSubview:self.myView];
}   

// After viewDidLoad is finished, mv is decallocated. 
// Now UIView object now have two pointer pointing to it. self.view points to it strongly hence the owner, while _myView points to it weakly. 

Answer 1

你大多是正確的，除了這句話：

viewDidLoad完成后，mv被解除分配。

那就是你錯了。 請記住，只有當retain對象的每個人release它時，才會發生對象的release 。 因此，當您release臨時變量mv ，您仍然有另一個來源保留它： self.view.subviews 。 一旦從子視圖數組中刪除mv ，就可以正確清理它，將_myView設置為nil ，並且不再有泄漏。