Adding space between textfield character when typing in text filed

Question

I have a textfield with maximum character range 16, After every 4 characters, I want to add minus character or space and then writing The rest of the characters

Answer 1

Use shouldChangeCharactersIn like this way.

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    if [6, 11, 16].contains(textField.text?.count ?? 0) && string.isEmpty {
        textField.text = String(textField.text!.dropLast())
        return true
    }
    let text = NSString(string: textField.text ?? "").replacingCharacters(in: range, with: string).replacingOccurrences(of: "-", with: "")
    if text.count >= 4 && text.count <= 16 {
        var newString = ""
        for i in stride(from: 0, to: text.count, by: 4) {
            let upperBoundIndex = i + 4
            let lowerBound = String.Index.init(encodedOffset: i)
            let upperBound = String.Index.init(encodedOffset: upperBoundIndex)
            if upperBoundIndex <= text.count  {
                newString += String(text[lowerBound.. 19 {
                   newString = String(newString.dropLast())
                }
            }
            else if i <= text.count {
                newString += String(text[lowerBound...])
            }
        }
        textField.text = newString
        return false
    }
    if text.count > 16 {
        return false
    }
    return true
}

Note: I have used - (Hyphen) you can simply replace it with Space if you want Space instead of - (Hyphen).

Edit: Code is edited to latest swift 4.*, for older swift version please check edit history.