Every application must have exactly one instance of UIApplication...

Question

From documentation...
""Every application must have exactly one instance of UIApplication (or a subclass of UIApplication )" .. none of the templates in the SDK create an app with an UIApplication instance or subclass that I can tell."
Yet, in all three sample templates I can't find any instance or subclass of UIApplication.
Creating a new Cocoa Touch Toolbar Project...the closest thing is:
@interface Untitled2AppDelegate : NSObject <UIApplicationDelegate> {...}
Does using the <UIApplicationDelegate> ake the NSObject an instance or subclass of UIApplication? Why not use
@interface Untitled2AppDelegate : UIApplication {...}

Answer 1

Check the main.m file. It should have a line something like this in it:
int retVal = UIApplicationMain(argc, argv, nil, @"Untitled2AppDelegate");
The UIApplicationMain function is creating a UIApplication instance internally and setting its UIApplicationDelegate to your custom delegate.
The 3rd parameter specifies the name of the UIApplication class you want to use. Passing nil defaults to the normal UIApplication class, but if you needed to use a custom class derived from UIApplication, you could pass its name in there. More than likely, though, the UIApplicationDelegate interface gives you access to everything you need.