title: Requesting a call back or notification once avaudioplayer completes it's playback
body: <p>I am working in audio player module where it takes one audio file and playing. I am using AvAudioPlayer to play my audio file, it's working as expected and I am getting call backs  once finished the audio playback. I have implemented looping by  <strong>numberOfLoops</strong> property with negative value so far it's good. In a case I need call back once the current audio finishes playing first time. Is there any possible way to get call back or observer to notify me my audio played first time.</p>
  
  <p>My idea is that we can achieve this by running a timer. What is the best approach?</p>
  
  <p><strong>Generic:</strong>
  Each time completion of audio play back expecting a notification even it has infinite loop also.</p>