title: Add a Clear button functionality in Custom Keyboard using Swift
body: <p>I use a custom keyboard which contains a delete and a clear button.I can able to delete the letters using this code</p>
  
  <pre><code>let obj =  UIInputViewController()
  (obj.textDocumentProxy as UIKeyInput).deleteBackward()
  </code></pre>
  
  <p>Is it any keyword available to clear whole text in a textfield.</p>
  
  <p>NB: I found <a href="https://stackoverflow.com/questions/1507731/custom-keyboard-clear-button">this</a> link but it is not apt for my requirement </p>