Migrating existing access tokens to Facebook iOS SDK 3.0
问题 I just overhauled my codebase to use the new facebook-ios-sdk 3.0 (from the previous version, 2.x or whatnot). Everything worked great, until I realized I hadn't accounted for users who had already granted the app permission/logged in with the previous implementation of the SDK. So I tried checking to see if the accessToken was saved in NSUserDefaults, and if so, make a call to open a session: if ([[NSUserDefaults standardUserDefaults] objectForKey:@"FBAccessTokenKey"] && [[NSUserDefaults