iOS：处理FBAppCall：如何验证用户是否发布了某些内容？

Question

我希望在授予应用内奖励之前，确保我的产品的用户实际上已共享我的应用所需的内容。

这是我想要处理 FBAppCall 回调的代码段。

- (BOOL)application:(UIApplication *)application openURL:(NSURL *)url
  sourceApplication:(NSString *)sourceApplication annotation:(id)annotation
{
    BOOL wasHandled = [FBAppCall handleOpenURL:url sourceApplication:sourceApplication];

    if(wasHandled){
    //This is a good place to reward the user.. would be good to be able to access sourceApplication and see if things have actually been posted. But I am not quiet sure how..
    }
    else{
        NSLOG(@"FB App did not handle the post so won't do anything.");
    }

    return wasHandled;
}

有什么建议吗？教程？