title: Merge inheritance realm objects together
body: <p>As you see below i have 2 Realm subclasses <code>Dog</code> and <code>Cag</code>, which contain a different amount of objects. i want to retrieve these objects and add them together in one array, so i can run the <code>sortPetByDate</code>. However i can't <code>appendTheContentOf</code>, due to the fact that </p>
  
  <pre><code>let cat = realm.objects(Cat)
  let dog = realm.objects(Dog)
  </code></pre>
  
  <p>returns <code>Results&lt;t&gt;</code>.</p>
  
  <p>What is the best way to run this method on multiple inheritance objects?</p>
  
  <pre><code>func sortPetByDate(array:[AnyObject]) -&gt; [AnyObject]     {
      return array.sort{ ($0.0 as! Pet).date.compare(($0.1 as! Pet).date) == NSComparisonResult.OrderedAscending }
  }
  </code></pre>
  
  <p>Example of my inheritance classes:</p>
  
  <pre><code>class Pet: Object {
      dynamic var date = NSDate()
      dynamic var title = String()
  }
  
  class Dog: Pet {
  }
  
  class Cat: Pet {
  }
  </code></pre>