title: How do I format UITextField text in real time, while it's being edited?
body: <p>How can I change value of <code>UITextField</code> text while typing?</p>
  
  <p>In other word:</p>
  
  <p>when I type 1 it should show 1</p>
  
  <p>when I type 10 it should show 10</p>
  
  <p>when I type 100 it should show 100
  but</p>
  
  <p>when I type 1000 it should show 1,000</p>
  
  <p>Can you give any idea?</p>