从AppDelegate中检测UIViewController的变化

Question

我试图执行一个函数，每次应用程序加载一个新的ViewController(过渡到不同的视图)。为了避免在每个ViewController中调用这个函数(大约有10个ViewController，还有更多要添加)，我希望在AppDelegate中通过添加某种观察者来做到这一点。这可能吗?或者它能以某种方式与UIViewController扩展的帮助?

Answer 1

或者你可以子类化UINavigationController并在你感兴趣的事件上发布通知:

class NotificationNavigationController: UINavigationController {
    override func pushViewController(_ viewController: UIViewController, animated: Bool) {
        NotificationCenter.default.post(name: Notification.Name(rawValue: "NavigationControllerWillPush"), object: nil)
        super.pushViewController(viewController, animated: animated)
    }
    override func popViewController(animated: Bool) -> UIViewController? {
        NotificationCenter.default.post(name: Notification.Name(rawValue: "NavigationControllerWillPop"), object: nil)
        return super.popViewController(animated: animated)
    }
}

然后在你的应用程序委托中，你可以观察到这些通知:

NotificationCenter.default.addObserver(forName: Notification.Name(rawValue: "NavigationControllerWillPush"), object: nil, queue: OperationQueue.main) {
            notification in
            // handle push
        }
NotificationCenter.default.addObserver(forName: Notification.Name(rawValue: "NavigationControllerWillPop"), object: nil, queue: OperationQueue.main) {
            notification in
            // handle pop
        }

Answer 2

忘记AppDelegate, observer或extensions，使用Inheritance。

你所有的uiviewcontroller应该扩展MainViewController基类，你可以把你的逻辑在基类的viewDidLoad方法(或viewDidAppear)。