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

Swift 2.3

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {

        let characters = ["#", "$", "!", "&","@"]
        for character in characters{
            if string == character{
                print("This characters are not allowed")
                return false
            }
        }
}