How to restrict certain characters in UITextField in Swift?

Question

I am creating a trivia application that asks for a username on start up. I\'d like to make it impossible to use characters such as #$@!^& etc (also including \"space\").

Answer 1

internal func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool{
     if let text = string{
           if text == "#" || text == "$" || text == "!"{ \\and so on
              return false
           }
     }
     return true
}