iPhone Text Field>Format Input String as a Credit Card Number As They Type

Question

How can I format a users text field input as they type and insert a "-" or " " on every 5th character.

4500000000000000 becomes 4500 0000 0000 0000

Answer 1

Make a delegate for your text field, then implement -textField:shouldChangeCharactersInRange:replacementString: to update the text field whenever the user types / pastes anything.