Integrating FB connect with Foursquare into an IPhone App

Does anyone know, whether/how it is possible to link your FB account to your Foursquare account within an own IPhone App? This is the functionality implemented by a lot of sites for th开发者_如何学Goeir Web services.

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The only thing I can think of is to come up with your own implementation. Basically have your own users table, when the user does a connect with facebook, you store his FBId in your users table. Later if he wants to connect his Foursquare account, you simply store his FS id also in the users table. For more flexibility you would have a users and a usernetworks table. Usernetworks could have the linked social networks in it.

This is the simplest solution I can think of.