willMoveToParentViewController: 和 didMoveToParentViewController: 到底是做什么的? [英] What exactly willMoveToParentViewController: and didMoveToParentViewController: do?

问题描述

我知道从 iOS5 和新的 UIViewController 包含方法开始，您应该将这些方法与 addChildViewController:、removeFromParentViewController: 和转换方法一起调用.我也知道在三种情况下调用它们的正确顺序.我不知道这些方法到底是做什么的?

I know that starting with iOS5 and the new UIViewController containment methods, you are supposed to call these methods together with addChildViewController:, removeFromParentViewController: and the transition method. I also know the proper order of calling them in the three scenarios. What I don't know is what exactly these methods do?

如果这些只是 UIViewController 子类的覆盖点，我想我们不需要在覆盖时调用 super.如果我在删除视图控制器或 didMoveToParentViewController: self 之前不调用 willMoveToParentViewController: nil 会/会出现什么问题?

If these were merely override points for subclasses of UIViewController I guess we wouldn't be required to call super when overriding. What can/will go wrong if I don't call willMoveToParentViewController: nil before removing a view controller or didMoveToParentViewController: self?

推荐答案

除了上面所说的，他们确实调用了一些委托方法:

In addition to what has been said, they do call some delegate methods:

addChildViewController 调用 [child willMoveToParentViewController:self]

和 removeFromParentViewController: 调用 [child didMoveToParentViewController:nil]

此外，他们还修改了 childViewControllers 属性，该属性包含一组子视图控制器.

Also, they modify the childViewControllers property, which holds an array of child view controllers.

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