Yes, UIApplication is a singleton, and uses the normal singleton pattern for Objective-C:
[UIApplication sharedApplication];
You can get your delegate class directly from it:
MyAppDelegate *delegate = (MyAppDelegate *)[[UIApplication sharedApplication] delegate];
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…