class ViewController: UIViewController, UITextFieldDelegate {

​

    @IBOutlet weak var textField: UITextField!

​

    override func viewDidLoad() {

        super.viewDidLoad()

​

        // you can set the following two properties for the text field in Interface Builder, if you'd prefer

​

        textField.delegate = self

        textField.keyboardType = .numberPad

    }

​

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

        let invalidCharacters = CharacterSet(charactersIn: "0123456789").inverted

        return string.rangeOfCharacter(from: invalidCharacters) == nil

    }

​

    // or, alternatively:

    //

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

    //     return string.range(of: "^\\d*$", options: .regularExpression) != nil

    // }

​

}

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

        let bytes: [Unicode.UTF8.CodeUnit] = Array([0x7F, 0x08, 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x2E, 0x2D])

        let newString = String(bytes: bytes, encoding: String.Encoding.utf8)!

        if let x = string.rangeOfCharacter(from: NSCharacterSet.init(charactersIn: newString) /* decimalDigits */ /* init(charactersIn: stringa) */ as CharacterSet) {

                return true

             } else {

             return false

          }

       }