title: What's the best way to validate currency input in UITextField?
body: <p>My application allows the user to enter a numeric value (currency) in a <code>UITextField</code> control, but the keyboard layout that I wish was available is unfortunately not one of the built-in options, so I had to choose the "Numbers &amp; Punctuation" option in Interface Builder. Here's the corresponding dialog window in IB:</p>
  
  <p><a href="https://i.stack.imgur.com/FbnvH.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/FbnvH.png" alt="enter image description here"></a></p>
  
  <p>So when my application asks the user for the input, it is displaying the following:</p>
  
  <p><a href="https://i.stack.imgur.com/u9tbB.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/u9tbB.png" alt="enter image description here"></a></p>
  
  <p>Which is perfectly fine, but look at all of the extra keys available to the user! One could easily enter "12;56!" in the text field, and I assume I have to validate that somehow.</p>
  
  <p>So my question is: how do I validate currency values entered into a <code>UITextField</code>?</p>