gistfile1.m

@interface MyAudioPlayer() {
  AVAudioPlayer* currentPlayer;
}
@end

@implementation MyAudioPlayer

+(instance_type)sharedPlayer {
  static MyAudioPlayer* sharedPlayer;
  static dispatch_once_t onceToken;
  dispatch_once(&onceToken, ^{
    sharedPlayer = [[MyAudioPlayer alloc] init];
  });
  return sharedPlayer;
}

-(void)playURL:(NSURL*)url {
  [currentPlayer stop];
  currentPlayer = [[AVAudioPlayer alloc] initWithURL: url];
  [currentPlayer prepareToPlay];
}

@end