title: How to resign first responder when entering currency
body: <p>I'd like to make my text field resign first responder after the cents are entered in a text field for entering currency. I'm using <code>UIKeyboardTypeDecimalPad</code> so only numerals are entered. When the second numeral after the decimal point is entered I want the text field to resign first responder.</p>
  
  <p>1</p>
  
  <p>12</p>
  
  <p>123</p>
  
  <p>123.4</p>
  
  <p>123.45 <em>now resign first responder</em>.</p>
  
  <p>Do I have the delegate compare the text to the regular expression <code>*\...</code> for each <code>textDidChange</code> notification? Starting counting when <code>.</code> is entered?</p>
  
  <p>Is there a way to apply <code>NSNumberFormatter</code> and <code>setMaximumFractionDigits:2</code> to the text input field?</p>