title: Enable/disable button depending on On Demand Resources tag
body: <p>I have some buttons linked to an <code>IBAction</code> that plays a sound.</p>
  
  <pre><code>-(IBAction)listen {
   // play the audio
  }
  </code></pre>
  
  <p>My files are organized with <a href="https://developer.apple.com/library/ios/documentation/FileManagement/Conceptual/On_Demand_Resources_Guide/Managing.html#//apple_ref/doc/uid/TP40015083-CH4-SW1" rel="nofollow">On Demand Resources</a>, and I have 3 tags:</p>
  
  <ul>
  <li>level1</li>
  <li>level2</li>
  <li>level3</li>
  </ul>
  
  <p>So what I'd like to achieve is:</p>
  
  <p><strong>if the user is on level 1, he will only be able to play files with the <code>level1</code> tag</strong>. If he clicks on a <code>level2</code> tag audio, an alert will appear.</p>
  
  <p>How can I check if a file has a specific tag?</p>