title: Game Center Invitation
body: <p>I am using Game Kit and I want to submit a score on Game Center. I did that but now I want to invite friends. How do I invite my friends and how do I see my friend's score? This code is for show leaderboard:</p>
  
  <pre><code>  - (IBAction) showLeaderboard
    {
       GKLeaderboardViewController *leaderboardController = [[GKLeaderboardViewController alloc] init];
       if (leaderboardController != NULL) 
       {
          leaderboardController.category = self.currentLeaderBoard;
          leaderboardController.timeScope = GKLeaderboardTimeScopeWeek;
          leaderboardController.leaderboardDelegate = self; 
          [self presentModalViewController: leaderboardController animated: YES];
       }
    }
  </code></pre>