ios - presentViewController 更改 KVO

Question

我正在尝试收听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）。UIViewController 中是否有办法在 UIViewController 主动呈现时监听更改？

Answer 1

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

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
}

斯威夫特 4：

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