title: ExtAudioFileOpenURL error: "Cannot convert the expression's type 'OSStatus' to type 'CFURL'"
body: <p>After spending several hours adamantly choosing to use Swift to open an extended audio file reference, I'm tempted to switch back to Objective C. I'm using the following code at the moment to try and open an audio file from a local path:
  </p>
  
  <pre><code>let audioURL:NSURL = NSURL(fileURLWithPath:"/my/file/path/here/song.mp3")
  var audioFileRef:Unmanaged&lt;ExtAudioFile&gt;?
  var error:OSStatus = ExtAudioFileOpenURL(audioURL as CFURL, audioFileRef)
  </code></pre>
  
  <p>Any idea on why I'm getting the following error?</p>
  
  <pre><code>"Cannot convert the expression's type 'OSStatus' to type 'CFURL'"
  </code></pre>