In the iPhone SDK, can anyone explain the difference between application DidFinishLaunching in delegate and ViewDidLoad method in ViewControler?
applicationDidFinishLaunching is called by the App Delgate when your application has finished launching. This method is useful for doing setup as soon as possible. Examples of this could include setting up GameCenter, and doing some first launch checking.
viewDidLoad is called by a UIViewController after the view is loaded, usually from the nib. However, in some cases, you may want to do setup before the view is loaded. In that case, use
viewWillLoad is called just before the view is loaded, usually from the nib. For the most part, it will not make much of a difference wether you use viewDidLoad or viewWillLoad. However, some setup may have to be done after the view is loaded and other setup you may want to do before the screen displays anything.
applicationDidFinishLaunching is for initial appwide setup, viewWillLoad is for setup before the view is displayed, and viewDidLoad is for setup right after the view is loaded.