title: Solve Bug in UITextField: When it is empty, Pressing backspace doesn't Trigger correct function
body: <p>Men, I don't believe that this will be a problem to me. If I press a key in keyboard, the UITextField delegate trigger the function: </p>
  
  <pre><code> - (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
         if ([string lenght]==0) NSLog("Backspace was pressed");
   }
  </code></pre>
  
  <p>But the problem is: when the text is empty and I press backspace, this function <code>IS NOT</code>  called. There are a way to detect the backspace was pressed in this situation? </p>
  
  <p>Or I will have to send this bug to Apple?</p>
  
  <p>Ps. I need this for the cursor go to previous UITextFild (if have one character and press backspace, it work)</p>