I'm diving into iPhone development and one of the core concepts im trying to get my head around is view controllers. If you look at the GLPaint example on the apple dev site, you'll see a project that has...

1. An app delegate class
2. A uiwindow subclass
3. And a uiview subclass

And the uiview subclass implements all the core graphics painting logic and handles the touch events. My questions are, why is there no view controller implemented to handle that view logic? Could you use a view controller to implement that logic or does it have to be implemented in the uiview subclass? And last, when should you use a view controller to implement the view logic code?

Thanks so much in advance for your help!