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"). I took a look at this post here but it is written entirely in Objective-C. Thanks in advance.

Answer 1

Swift 4 iOS 11.2.x based on using an extension, tests to see if a string is a valid hex number in this example.

extension String {

var containsValidCharacter: Bool {
    guard self != "" else { return true }
    let hexSet = CharacterSet(charactersIn: "1234567890ABCDEFabcdef")
    let newSet = CharacterSet(charactersIn: self)
    return hexSet.isSuperset(of: newSet)
  }
}

You use it like with the UITextFieldDelegate.

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    return (string.containsValidCharacter)
}

Although I read in an earlier post that CharacterSets do not support characters that are composed of more than one Unicode.Scalar; so use with caution I guess.

Answer 2

Since you're explicitly asking for Swift, I've translated the top asnwer in the linked question.

let notAllowedCharacters = " ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_.";

func textField(
    textField: UITextField,
    shouldChangeCharactersInRange range: NSRange,
    replacementString string: String)
    -> Bool
{
    let set = NSCharacterSet(charactersInString: notAllowedCharacters);
    let inverted = set.invertedSet;

    let filtered = string
        .componentsSeparatedByCharactersInSet(inverted)
        .joinWithSeparator("");
    return filtered != string;

}

Answer 3

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
}

Answer 4

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
            }
        }
}