title: How to wait for UITextField becomeFirstResponder before insertText?
body: <p>How to wait for <code>UITextField</code> <code>becomeFirstResponder</code> before <code>insertText</code>?</p>
  
  <ul>
  <li>A <code>UITextField</code> is the first responder.  </li>
  <li>Then a modal view pops up and kills the <code>UITextField</code> focus (keyboard is gone)</li>
  <li>The modal view finishes and notifies via <code>delegate.thingsDone</code></li>
  <li><code>delegate.thingsDone</code> tries to <code>insertText</code> into the <code>UITextField</code> ...</li>
  <li>(Oops, the <code>UITextField</code> is not the first responder yet)</li>
  </ul>
  
  <p>The situation is, I have a <code>NSString *</code> in hand and wants to <code>insertText</code> into the <code>UITextField</code> <strong><em>as soon as</em></strong> it <code>becomeFirstResponder</code>.</p>
  
  <p>What is the proper way to do it?</p>