title: Gaming Center iphone-sdk, how to get current player's nickname?
body: <p>When my app start it should promt user to log into gaming center so that I can retrieve his nickname and then use it later to display his name,
  I have the following code which somehow worked once:</p>
  
  <pre><code>- (void) authenticateLocalPlayer
  {
      GKLocalPlayer *localPlayer = [GKLocalPlayer localPlayer];
      [localPlayer authenticateWithCompletionHandler:^(NSError *error) {
          if (localPlayer.isAuthenticated)
          {
              // Perform additional tasks for the authenticated player.
          }
      }];
  
  }
  </code></pre>
  
  <p>It showed a alert view with and some buttons, but it doesn't work. Help, maybe there's an easier way to retrieve current player's nickname. Thanks!!</p>