title: Xcode spurious warnings for "Creating selector for nonexistent method 'compare:'"
body: <p>Here's a snippet:</p>
  
  <pre><code>NSArray *a = [@[@"a", @"b", @"c"] sortedArrayUsingSelector:@selector(compare:)];
  </code></pre>
  
  <p>XCode (5.0) is giving me the following warning:</p>
  
  <pre><code>Creating selector for nonexistent method 'compare:'
  </code></pre>
  
  <p>How do I eliminate these warnings?</p>