How to Lock and Unlock contents on In-App-Purchasing?

I am just trying to implement In-App-Purchasing with开发者_Go百科 in my application and I am successfully able to test my application but I want to offer few part of application will be free and some part will be give to user after payment. How can I do it. Thank you.

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we basically keep the features locked in our application and unlock them after user makes in app purchase. To lure the user, when user tries to access that feature, we usually show the user message that it is locked in this version of application and in order to unlock it, in app purchase needs to be done.

All the features should have unique product identifier, so as to identify which feature the user unlocked (purchased)