title: Elegant way to extend MDLAsset to support importing new formats
body: <p>I was wondering what would be an elegant way, in Swift, to make MDLAsset to support to other 3D model files than the default ones.  </p>
  
  <p>My best finding is to use a factory method like this:</p>
  
  <pre><code>extension MDLAsset {
      static func makeAssetFromEXTFile(atUrl: URL) -&gt; MDLAsset { … }
  }
  </code></pre>
  
  <p>Of course I thought about overriding initialisers but since there are many of them I don't really know if that's the right way to go...  </p>
  
  <p>Do you think my factory function method is good? Do you see any other elegant solution? :)  </p>
  
  <p>Thank you</p>