title: How to extend protocols / delegates in Objective-C?
body: <p>If i want to extend a class like AVAudioPlayer, whats the best way to also add another method to AVAudioPlayerDelegate?</p>
  <p>Should I make a category for it, do I extend it?</p>
  <p>If I extend it do I then also have to make sure to overwrite the actual delegate getter/setter?  How would I extend the protocol?</p>
  <p>The following gives me errors</p>
  <pre><code>@protocol AudioTrackDelegate : AVAudioPlayerDelegate {
      - (void)foo;
  }
  @end
  
  @interface AudioTrack : AVAudioPlayer {
  }
  @end
  </code></pre>