title: Set maximum characters (to one) in a NSTextfield in Swift
body: <p>How do i set the maximum amount of characters in multiple NSTextfields (OSX cocoa app, NOT iOS) to one in Swift? </p>
  
  <p>Please explain how to do it, because I'm a complete newbie when it comes to OSX app development and therefore I don't understand short answers like "Use NSFormatter", because I have no idea what it is and how to implement it. Like Examples</p>