title: Which event is used to detect the UITextfield in null state
body: <p>i'm trying develop a textfield switching from 1 to another automatically, similarly i can switch the textfield backwards, but in null state i can't switch the cursor into the previous textfield , i tried with <strong>EditingChange Event</strong> but when the textfield in null state the <strong>Editng Change</strong> function is not fired.</p>
  
  <p>The code is :</p>
  
  <pre><code>@IBAction func textFieldEditingChanged(_ sender: UITextField) {
  
      if(sender.text?.characters.count == 1) {
          switch sender {
          case otpField1:
              otpField2.becomeFirstResponder()
          case otpField2:
              otpField3.becomeFirstResponder()
          case otpField3:
              otpField4.becomeFirstResponder()
          case otpField4:
              otpField4.resignFirstResponder()
          default:
              break
          }
      }else {
  
      }
  
      if ((sender.text?.characters.count)! &lt;= 0 || sender.text! == "" || sender.text?.isEmpty == true) {
  
          switch sender {
          case otpField4:
              otpField3.becomeFirstResponder()
          case otpField3:
              otpField2.becomeFirstResponder()
          case otpField2:
              otpField1.becomeFirstResponder()
          case otpField1:
              otpField1.resignFirstResponder()
          default:
              break
  
          }
      }
  
  }
  </code></pre>