title: Enum value and predicates
body: <p>Is there a way to use an enum value in an <code>NSPredicate</code> without calling <code>rawValue</code>?</p>
  
  <p>For example:</p>
  
  <pre><code>enum MyEnum: Int32 {
      case A, B, C
  }
  
  var predicate: NSPredicate = NSPredicate(format: "prop_status == %i",
                                           argumentArray: [MyEnum.A])
  </code></pre>
  
  <p>I was thinking about extending <code>NSPredicate</code> so that it can handle <code>MyEnum</code> but not sure how to do that.</p>