title: How to add hyphen after every 4th character to a string in iOS
body: <p>I using card.io for scanning my credit/debit card. When the scan is completed I receive string like <code>'3456789023456789'</code>. I am setting this string value to my textfield. Now I want that when setting the string value to textfield it should appear in this format <code>'3456-7890-2345-6789'</code>.</p>