Objective-C:理解 ARC

Question

我是 Objective-C 的新手。这是我对一些用于以编程方式添加 subview 的简单代码的 ARC 的理解(如在评论中)。如果我错了，请纠正我。特别是在这个声明中:

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

// _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

你大部分是正确的，除了这句话:

After viewDidLoad is finished, mv is decallocated.

那就是你错了。请记住，对象的解除分配只有在每个人 retain 时才会发生。是对象 release是的。因此，虽然你有 release 'd 临时变量 mv , 您还有另一个来源保留它: self.view.subviews .一次 mv从 subview 数组中删除，可以正确清理， _myView设置为 nil ，并且您没有更多的泄漏。