title: Swift accessing nested array element specified by `NSIndexPath`
body: <p>If I have nested arrays like this:</p>
  
  <pre><code>array[0].children[0].children[0].children[2]
  </code></pre>
  
  <p>How can I access one of the nested elements? I know the <code>NSIndexPath</code> type exists to represent an index path into nested arrays, but how can I access the element specified by a given <code>NSIndexPath</code>?</p>