title: iOS - Attempting to play mp3 file fails
body: <p>I'm trying to playback and mp3 file I retrieve from my server from my app doing the following:</p>
  
  <pre><code>- (IBAction)play:(UIButton *)sender {
      dispatch_queue_t downloadQueue = dispatch_queue_create("audio data downloader", NULL);
      dispatch_async(downloadQueue, ^{
          NSURL *audioURL = [NSURL URLWithString:[NSString stringWithFormat:@"%@%@/%@.mp3", FONYK_FILES_URL, [self.voicenote valueForKeyPath:@"Fonyker.fonykid"], [self.voicenote valueForKeyPath:@"Voicenote.vnid"]]];
          NSData *audioData = [NSData dataWithContentsOfURL:audioURL];
  
          dispatch_async(dispatch_get_main_queue(), ^{
              NSError *error = nil;
              AVAudioPlayer *audioPlayer = [[AVAudioPlayer alloc] initWithData:audioData error:&amp;error];
              NSLog(@"%@", error);
              audioPlayer.delegate = self;
              [audioPlayer play]; 
          });
      });
  }
  </code></pre>
  
  <p>The playback fails, meaning no sound is emitted and I get this output when debugging my app step by step:</p>
  
  <pre><code>Catchpoint 2 (exception thrown).Single stepping until exit from function __cxa_throw, which has no line number information. 
  </code></pre>
  
  <p>And this comes up when I NSLog the error in the simulator:</p>
  
  <pre><code>Error Domain=NSOSStatusErrorDomain Code=-50 "The operation couldn’t be completed. (OSStatus error -50.)"
  </code></pre>
  
  <p>Nothing else shows it just fails, any thoughts?</p>
  
  <p><strong>UPDATE:</strong> Modified my code as per J_D's answer and got this in the simulator:</p>
  
  <pre><code>Error loading /System/Library/Extensions/AudioIPCDriver.kext/Contents/Resources/AudioIPCPlugIn.bundle/Contents/MacOS/AudioIPCPlugIn:  dlopen(/System/Library/Extensions/AudioIPCDriver.kext/Contents/Resources/AudioIPCPlugIn.bundle/Contents/MacOS/AudioIPCPlugIn, 262): Symbol not found: ___CFObjCIsCollectable
    Referenced from: /System/Library/Frameworks/Security.framework/Versions/A/Security
    Expected in: /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator5.1.sdk/System/Library/Frameworks/CoreFoundation.framework/CoreFoundation
   in /System/Library/Frameworks/Security.framework/Versions/A/Security
  2012-04-17 15:03:43.054 Fonyk[8238:15307] Error loading /System/Library/Extensions/AudioIPCDriver.kext/Contents/Resources/AudioIPCPlugIn.bundle/Contents/MacOS/AudioIPCPlugIn:  dlopen(/System/Library/Extensions/AudioIPCDriver.kext/Contents/Resources/AudioIPCPlugIn.bundle/Contents/MacOS/AudioIPCPlugIn, 262): Symbol not found: ___CFObjCIsCollectable
    Referenced from: /System/Library/Frameworks/Security.framework/Versions/A/Security
    Expected in: /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator5.1.sdk/System/Library/Frameworks/CoreFoundation.framework/CoreFoundation
   in /System/Library/Frameworks/Security.framework/Versions/A/Security
  </code></pre>
  
  <p><strong>UPDATE:</strong> the real issue I had was not creating and AVAudioSession instance set to playback in my code, doing so along with the corrections answer I accepted made it work.</p>