判断当前视图控制器是怎么来的

作者：知乎用户
链接：https://www.zhihu.com/question/26485743/answer/33062225
来源：知乎
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早在 iOS 5 的时候 UIViewController 就已经提供了四个方法来满足你的需求：

/*
  These four methods can be used in a view controller's appearance callbacks to determine if it is being
  presented, dismissed, or added or removed as a child view controller. For example, a view controller can
  check if it is disappearing because it was dismissed or popped by asking itself in its viewWillDisappear:
  method by checking the expression ([self isBeingDismissed] || [self isMovingFromParentViewController]).
*/

- (BOOL)isBeingPresented NS_AVAILABLE_IOS(5_0);
- (BOOL)isBeingDismissed NS_AVAILABLE_IOS(5_0);

- (BOOL)isMovingToParentViewController NS_AVAILABLE_IOS(5_0);
- (BOOL)isMovingFromParentViewController NS_AVAILABLE_IOS(5_0);

有一点需要注意的是如果你是 present 到一个 UINavigationController 的时候，你应该使用后两个方法。

还有别的方法，比如检查 push 或 pop 可以实现 UINavigationController 的代理方法：

- (void)navigationController:(UINavigationController *)navigationController willShowViewController:(UIViewController *)viewController animated:(BOOL)animated;

检测 present 或 dismissed 可以逐级检查 UIViewController 的 presentingViewController 属性等。