问题描述
我只是想了解UIApplication的一般体系结构。我对使用委托的理解如下：
protocol MyDelegate {
func someProtocolMethod()
}
class SomeClass {
var delegate: MyDelegate!
init(){
}
func someClassMethod(){
self.delegate.someProtocolMethod()
}
}
class ClassConformingToDelegate: NSObject,MyDelegate {
let someClass: SomeClass
override init(){
someClass = SomeClass()
super.init()
someClass.delegate = self // self has to be assigned so that SomeClass's delegate property knows what the conforming class is
}
func someProtocolMethod(){}
}
以类似的方式，AppDelegate通过实现多种协议方法来符合UIApplicationDelegate。
class AppDelegate: UIResponder,UIApplicationDelegate {
func application(_ application: UIApplication,didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
// Override point for customization after application launch.
return true
}
// MARK: UISceneSession Lifecycle
func application(_ application: UIApplication,configurationForConnecting connectingSceneSession: UISceneSession,options: UIScene.ConnectionOptions) -> UISceneConfiguration {
// Called when a new scene session is being created.
// Use this method to select a configuration to create the new scene with.
return UISceneConfiguration(name: "Default Configuration",sessionRole: connectingSceneSession.role)
}
func application(_ application: UIApplication,didDiscardSceneSessions sceneSessions: Set<UISceneSession>) {
// Called when the user discards a scene session.
// If any sessions were discarded while the application was not running,this will be called shortly after application:didFinishLaunchingWithOptions.
// Use this method to release any resources that were specific to the discarded scenes,as they will not return.
}
}
UIApplication在其类中声明如下：
unowned(unsafe) var delegate: UIApplicationDelegate?
但是，为了使此委托人知道AppDelegate.swift是真正的委托人，必须实例化UIApplication并将AppDelegate.swift分配给实例，类似于上面的示例。因此，AppDelegate.swift之内应该发生以下情况：
let application = UIApplication()
application.delegate = self
但是，该步骤如何省略，AppDelegate仍然有效？
解决方法
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