问题描述
假设我有 UIViewController A和B.
用户使用push segue从A导航到B.
比用户按下后退按钮并进入A.
Say I have UIViewController A and B.User navigates from A to B with a push segue. Than user presses back button and comes to A.
现在调用A的 viewWillAppear 。我可以在这里的代码中知道我来自后退按钮（ navigationController popTo ... ）而不是通过其他方式？而且无需在B视图控制器中编写特殊代码。
Now viewWillAppear of A is called. Can I know in the code here that I came from back button (navigationController popTo...) and not by another way? And without writing special code in the B view controller.
推荐答案
嗯，也许你可以在<$中使用 self.isMovingToParentViewController c $ c> viewWillAppear ，请参阅，如果是 NO 则表示当前视图控制器已经在导航堆栈上。
hm, maybe you can use self.isMovingToParentViewController in viewWillAppear, see docs, if it is NO then it means the current view controller is already on the navigation stack.
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