How to add "in app purchase" code in iPhone SDK?

I want to use "in app purchase" for trial version of my application. But I don't have a clear idea about "in app purchase". My problem is how to implement "in 开发者_如何学编程app purchase" in my application and uploading process. I have already uploaded a full version of the application. Please help me.

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Well, the best way to understand the InApp process is to read the Apple rules about it at http://developer.apple.com/ Everything about how to implement it in your application is described over there. See for example: https://developer.apple.com/library/ios/#documentation/NetworkingInternet/Conceptual/StoreKitGuide/Introduction/Introduction.html

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Cheers