textfield function

gistfile1.txt

    func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
        
        if let digit = Int(string) {
            amount = amount * 10 + digit
            textField.text = String(describing: currencyAmount()!)
        } else if string == "" {
            amount = amount / 10
            textField.text = String(describing: currencyAmount()!)
        }

        return false
    }
}