Question

我是Objective-C的新手。以下是关于ARC的一些简单代码的理解（如在注释中），用于以编程方式添加子视图。如果我错了，请纠正我。特别是在这个声明中：

“ViewController弱点指向myView”ACTUALLY表示_myView （ViewController的ivar）弱点指向UIView对象

// _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

除了这句话外，你大多是正确的：

viewDidLoad完成后，mv被解除分配。

那就是你错了。请记住，只有当retain是对象release的所有人时，才会发生对象的释放。因此，虽然临时变量release有mv，但您还有另一个来源保留它：self.view.subviews。从子视图阵列中删除mv后，可以正确清理它，_myView设置为nil，并且您不会再有泄漏。

Objective-C：理解ARC

1 个答案: