title: Wait for UITableView to finish insert
body: <p>I'm trying to insert a new row, and immediately make it the first responder.</p>
  <p>Using <code>.insertRows()</code> seems to execute asynchronously, even with <code>.none</code>. for the animation. That means that when I call <code>cellForRow(at:)</code>, it returns nil.</p>
  <p>What would be the best way to wait for the insert to finish, before calling <code>becomeFirstResponder</code>?</p>
  <p>This does not work:</p>
  <pre class="lang-swift prettyprint-override"><code>self.tableView.insertRows(at: [newIndex], with: .none)
  self.tableView.cellForRow(at: newIndex)?.becomeFirstResponder() //Returns nil
  </code></pre>