问题描述
有许多众所周知的解决方案，用于检测视图控制器何时在向后导航过程中从屏幕上消失，由 UINavigationController 管理(即，当视图控制器从导航堆栈中弹出).换句话说，在源视图控制器中检测到向后导航.
There are a number of well known solutions for detecting when a view controller is in the process of disappearing off the screen in the process of a backwards navigation, managed by a UINavigationController (i.e. when a view controller is being popped off the navigation stack). In other words detecting a backwards navigation within the source view controller.
相比之下，我需要在 destination 视图控制器的 viewWillAppear 中检测到向后导航.或者换一种说法，检测由于 UINavigationController pop的结果，何时将显示视图控制器.
In contrast, I need to detect a backwards navigation within viewWillAppear for the destination view controller. Or to put it another way, detect when a view controller is about to be displayed as a result of a UINavigationController pop.
最简单/最简单的方法是什么?实现 UINavigationControllerDelegate 并设置一个标志可能是一种方法，但如果可能的话，宁愿避免可变状态.
What is the cleanest/simplest way to achieve this? Implementing UINavigationControllerDelegate and setting a flag might be one approach, but would rather avoid mutable state if possible.
我没有使用Storyboard来管理这两个屏幕之间的过渡.
I am not using Storyboards to manage the transition between these two screens.
推荐答案
签出UIViewController的此属性:P
Checkout this property of UIViewController :P
isMovingToParentViewController
isMovingFromParentViewController
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