title: Correct response to remote player quit in Game Center
body: <p>I have a turn-based match with two participants, <em>A</em> and <em>B</em>. It is currently <em>A</em>'s turn. <em>B</em> quits out of turn by calling:</p>
  
  <pre><code>[match participantQuitOutOfTurnWithOutcome:GKTurnBasedMatchOutcomeQuit ... etc.
  </code></pre>
  
  <p>As far as <em>A</em>'s Game Center app is concerned, the match with <em>B</em> is still in play – the match status is <code>GKTurnBasedMatchStatusOpen</code>, and the match outcomes are <code>GKTurnBasedMatchOutcomeNone</code> and <code>GKTurnBasedMatchOutcomeQuit</code> respectively.</p>
  
  <p>From the documentation, it appears that participant <em>A</em> should detect this and call:</p>
  
  <pre><code>participantA.matchOutcome = GKTurnBasedMatchOutcomeWon;
  participantB.matchOutcome = GKTurnBasedMatchOutcomeQuit;
  
  [self endMatchInTurnWithMatchData: ... etc.
  </code></pre>
  
  <p>However, there seems to be no notification for <code>participantQuitOutOfTurnWithOutcome</code>, and periodically iterating through each match to end turns feels like a kludge.</p>
  
  <p>What is the correct approach to ending these matches?</p>