title: How to suppress Xcode "Attribute Unavailable" warning in XIB file?
body: <p>My App is targeted to 10.6 and the "Deployment" value for all .xib files was 10.6 apart from one, which recently changed to 10.7 (I don't know when).  If I change it back to 10.6 I get the following warning from Xcode:</p>
  
  <pre><code>/Users/andy/Source/.../Preferences.xib:383: Identifier on OS X versions prior to 10.7
  </code></pre>
  
  <p>Here is the relevant part of the .xib file:</p>
  
  <pre><code>381: &lt;string key="NSFrame"&gt;{{1, 1}, {116, 104}}&lt;/string&gt;
  382: &lt;reference key="NSSuperview" ref="14642427"/&gt;
  383: &lt;reference key="NSNextKeyView" ref="1001986100"/&gt;
  384: &lt;string key="NSReuseIdentifierKey"&gt;_NS:11&lt;/string&gt;
  </code></pre>
  
  <p>(In fact when I open the .xib in BBEdit in order to see the warning line and then close it and clean/build in Xcode, the line being warned seems to change; it's always 383 however the content moves.  The last time the warning happened it was the <code>NSSuperview</code> line that was on line 383, which is weird to say the least).</p>
  
  <p>Sometimes I get two warnings.  The other warning is:</p>
  
  <pre><code>file://localhost/Users/andy/Source/.../Preferences.xib: warning: Attribute Unavailable: Identifier on OS X versions prior to 10.7
  </code></pre>
  
  <p>Which highlights a custom view in the .xib file when I click on it.</p>
  
  <p>Can anyone tell me what this warning means and how I get rid of it?</p>
  
  <p>I am developing under 10.8 using Xcode 4.4.1 and I reckon this warning will cause issues when running under 10.6 (something I cannot do during development).  I am happy to provide additional info, as required.</p>