ios - presentedViewController 更改 KVO

Question

我正在尝试监听 presentedViewController 的更改，但看起来该属性不符合 KVO(或者至少我无法从中获取更改)。当 UIViewController 被主动呈现时，UIViewController 中有没有办法监听变化？

Answer 1

presentedViewController 似乎不符合 KVO，但可以通过覆盖 UIViewController 的相关呈现/解除方法来通知更改:

override func presentViewController(viewControllerToPresent: UIViewController, animated flag: Bool, completion: (() -> Void)?) {
    // will present view controller
    super.presentViewController(viewControllerToPresent, animated: flag, completion: completion)
}

override func dismissViewControllerAnimated(flag: Bool, completion: (() -> Void)?) {
    super.dismissViewControllerAnimated(flag, completion: completion)
    // did dismiss view controller
}

swift 4:

override func dismiss(animated flag: Bool, completion: (() -> Void)? = nil) {
...
}