title: SLComposeViewController on Twitter: how to detect duplicate post
body: <p>I'm using Social Framework on iOS 6 for Twitter integration, using the following code :</p>
  
  <pre><code>SLComposeViewController *controller = [SLComposeViewController composeViewControllerForServiceType:SLServiceTypeTwitter];
  controller.completionHandler = ^(SLComposeViewControllerResult result) {
      if (result == SLComposeViewControllerResultCancelled) {
        // cancelled
      } else if (result == SLComposeViewControllerResultDone) {
        // done
      } else {
        // unknown
      }
      [controller dismissViewControllerAnimated:YES completion:nil];
  };
  [self presentViewController:controller animated:YES completion:Nil];
  </code></pre>
  
  <p>If the user set the same tweet message as one of its old message, I get a popup "The tweet "xxx" is a duplicate and cannot be sent." but the completion handler result value is  still SLComposeViewControllerResultDone. Is there a way to know if a tweet has <strong>really</strong> be sent ?
  It seems that the same behaviour is happening for TWTweetComposeViewController.</p>