Which site is the best for wiki of IOS, Cocoa, Objective-C?

Which site is the best for wiki开发者_StackOverflow社区 documentation of iOS, Cocoa and Objective-C?

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I heard this book is good: Programming in Objective-C 2.0 (2nd Edition)

you can try this videos:

Programming in Objective-C 2.0 LiveLessons (Video Training):Part I: Language Fundamentals and Part II: iPhone Programming and the Foundation Framework

http://www.informit.com/store/product.aspx?isbn=9780321720337

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Apples developer center docs? That's where I'd look first.