问题描述
我正试图了解对象生存期和引用计数如何与代码块交互。在下面的代码中,我只是做一个简单的动画,当UINavigationController的堆栈顶视图被交换时闪烁。棘手的部分是弹出的视图控制器是定义此代码的视图。
I'm trying to get my head around how object lifetime and reference counting interact with code blocks. In the following code I'm just doing a simple animation that flashes as the top view on a UINavigationController's stack is swapped. The tricky part is that the popped view controller is the one where this code is defined.
[UIView animateWithDuration:0.2
animations:^{self.navigationController.view.alpha = 0.0;}
completion:^(BOOL finished){
UINavigationController *navController = self.navigationController;
[self.navigationController popViewControllerAnimated:NO];
[navController pushViewController:nextView animated:NO];
[nextView release];
[UIView animateWithDuration:0.2
animations:^{navController.view.alpha = 1.0;}];
}];
我的问题是(忽略动画的样子),这是正确的方法吗?内存管理的角度。特别是:
My question is (ignoring what the animation looks like), is this the correct way to do this from a memory management perspective. In particular:
(1)当使用这种方法进行pop + push循环时,是否正确不再需要保留self,如不使用块?
(1) When using this approach for the pop+push cycle, is it correct that it is no longer necessary to retain self, as in other similar examples that do not use blocks?
(2)使用这些块调用animateWithDuration:...是否保留定义视图控制器(self),直到块执行?
(2) Does invoking animateWithDuration:... with the these blocks retain the defining view controller (self) until the blocks execute?
推荐答案
这是正确的。如果nextView是局部变量,这些块会自动保留self,navController和nextView。
It is correct. These blocks automatically retain self, navController and nextView if nextView is local variable.
这些块通过此方法从堆栈复制到堆中。这些块在执行后被释放。然后self,navController和nextView从这些块中释放。
These blocks are copied to heap from stack by this method. And these blocks are released after execution. And then self, navController and nextView are released from these blocks.
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