ios - 扩展 UIApplicationDelegate 协议(protocol)

Question

我想扩展 UIApplicationDelegate 协议(protocol)并为 application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool 方法提供默认实现.但是，我提供的默认实现不会被调用。

是否有可能扩展 UIApplicationDelegate 协议(protocol)(关于 UIApplication 是单例，或者协议(protocol)方法是可选的)，或者我做错了什么？

谢谢

AppDelegate.swift:

import UIKit
extension UIApplicationDelegate{
    func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
        print("does not print anything on launch.")
        return true
    }
}

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?
}

Answer 1

事实证明，您无法通过扩展为 Objective-C 协议(protocol)提供默认实现。有关协议(protocol)扩展限制的详细列表，请参见下面的链接。

https://www.captechconsulting.com/blogs/ios-9-tutorial-series-protocol-oriented-programming-with-uikit

What we CAN'T do: Provide default implementations for Objective-C protocols.