Mach-O Linker (Id) Error

I have just added the Google Tools for Mac OAuth classes to a project and get the following linker error

Any ideas what I need to do? It is an iPad app if that开发者_Python百科 makes any difference.

Thanks for your help :-)

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The error is a result of redefining a symbol in your RootViewController. There are few possible reasons for this.

1. In RootViewController you explicitly defined kGTMOAuth2ServiceProviderGoogle
2. You used #include instead of #import
3. You #import or #include the implementation file (.m)