playWaveformNamed:withCompletionHandler:

- (AVAudioPlayer *)playWaveformNamed:(NSString *)fileName
               withCompletionHandler:(void (^)(void))completionHandler
{
  NSString *filePath = [[NSBundle mainBundle] pathForResource:fileName ofType:@"wav"];
  NSURL *fileURL = [NSURL fileURLWithPath:filePath];
  AVAudioPlayer *audioPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:fileURL
                                                                      error:nil];
  audioPlayer.delegate = self;
  [audioPlayer play];
  
  AVURLAsset *audioAsset = [AVURLAsset URLAssetWithURL:fileURL options:nil];
  CMTime audioDuration = audioAsset.duration;
  float audioDurationSeconds = CMTimeGetSeconds(audioDuration);
  dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(audioDurationSeconds * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
    if (completionHandler) completionHandler();
  });
  return audioPlayer;
}