title: Mask numeric input in UITextField with Unit
body: <p>I have created an UITextField with UIKeyboardTypeNumberPad:</p>
  
  <pre><code>tf = [self makeTextField:self.groesse placeholder:@"erforderlich"];
  [tf setKeyboardType:UIKeyboardTypeNumberPad];
  </code></pre>
  
  <p>Now, I am trying to mask the entered number, that it will be shown for example like <code>187 cm</code> in the UITextField. I have tried it with </p>
  
  <pre><code>- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange (NSRange)range replacementString:(NSString *)string {
      if(textField == groesseField_) {
          textField.text = [NSString stringWithFormat:@"%@ cm",string];
          return NO;
      }
      return YES;
  }
  </code></pre>
  
  <p>But now, I am only able to input one digit instead of three for the example above.</p>
  
  <p>Can someone help me, what I am doing wrong? - Thanks.</p>