Why not subclass UIApplication? Why use a delegate?

Question

Instead of using an application delegate so that the `UIApplication` singleton can call the delegate methods at predefined time, what are the advantages and disadvantages of just subclassing `UIApplication`? (update: why does the iOS architecture use the application delegate instead of letting people write an application by subclassing `UIApplication` and overriding its various methods?) That's because when we create a new `UIView` control, we subclass `UIView` (update: or we subclass `UIViewController` too). So why for the case of application, we don't subclass `UIApplication` but use delegation instead?

Accepted Answer

Again, from the documentation:

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.

Why not subclass UIApplication? Why use a delegate?

Solution

Problem