title: Custom UITextField Delegate method shouldChangeCharactersIn is not getting called
body: <p>In my custom <code>UITextField</code>, <code>textFieldDidBeginEditing()</code> and <code>textFieldDidEndEditing()</code> delegate methods are getting called but 
  <code>func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -&gt; Bool</code></p>
  
  <pre><code>@IBDesignable class CustomUITextField: UITextField, UITextFieldDelegate{
  
     //getting Called
     @objc func textFieldDidBeginEditing() {
  
      }
  
     //getting Called
      @objc func textFieldDidEndEditing(){
  
      }
  
      //Not getting Called
      @objc func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -&gt; Bool {
  
      }
  
  }
  </code></pre>
  
  <p>I don't know why is not getting called. Any extra work needs to be done for that?</p>
  
  <p>Thanks in advance.</p>