The documentation I found recommends using [FBAppCall handleOpenURL:sourceApplication:withSession:] If the tutorial is using outdated code, you may come across more problems so I recommend finding a newer one.
Using this method in your code:
- (BOOL)application:(UIApplication *)application openURL:(NSURL *)url sourceApplication:(NSString *)sourceApplication annotation:(id)annotation {
return [FBAppCall handleOpenURL:url sourceApplication:sourceApplication];
}