iphone - 为什么不继承 UIApplication？为什么要使用委托(delegate)？

Question

与其使用应用程序委托(delegate)以便 UIApplication 单例可以在预定义的时间调用委托(delegate)方法，不如将 UIApplication 子类化的优点和缺点是什么？ (更新:为什么 iOS 架构使用应用程序委托(delegate)而不是让人们通过继承 UIApplication 并覆盖其各种方法来编写应用程序？)

那是因为当我们创建一个新的 UIView 控件时，我们继承了 UIView (update: 或者我们继承了 UIViewController 也是)。那么，为什么对于应用程序的情况，我们不继承 UIApplication 而是使用委托(delegate)呢？

Answer 1

同样，来自文档:

Subclassing Notes

You might decide to subclass UIApplication to override sendEvent: or sendAction:to:from:forEvent: to implement custom event and action dispatching. However, there is rarely a valid need to extend this class; the application delegate (UIApplicationDelegate is sufficient for most occasions. If you do subclass UIApplication, be very sure of what you are trying to accomplish with the subclass.