Is the AppNameAppDelegate.h and .m the entry points for all apps?

I'm looking at the source for: https://github.com/intabulas/ipivotal/blob/master/Classes/iPivotalAppDelegate.m

It looks like the "main" file for an iphone app, since it has a reference to the UIApplication, am I correct?

How is it that there is a .h file and in the .m file there is another block of code for the @interface with the same name?

I guess its allowed to redefine or continue the dec开发者_如何转开发laration of an interface?

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You're basically correct, -[<UIApplicationDelegate> applicationDidFinishLaunchingWithOptions:] is the entry point for an application's custom code (the real entry point is actually UIApplicationMain(), but I wouldn't try re-implementing that if I were you).

The "second @interface" in the .m file is a category, which allows you define extra methods that aren't defined in the class's main interface. This can be used either to break a class over multiple files, to add functionality to an existing class or (as here) to keep some method definitions private.

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In general, yes, the AppNameAppDelegate class is where you put all the application-level code.

What happens below the covers is that the main() function calls the Cocoa framework's initialization function, which loads a NIB that contains the app delegate. The UIApplication object (supplied by the framework) will invoke methods of the app delegate at appropriate times.

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You can continue defining the @interface in the .m file in a private category, this is commonly done to have private methods and properties you do not wish to expose.