textField.characther range

ViewController: UIViewController, UITextFieldDelegate {
	//create textfield view constructor
  let myTextField : UITextField = {
        let textField = UITextField()
        textField.backgroundColor = .white
        textField.translatesAutoresizingMaskIntoConstraints = false
        return textField
    }()
  
  override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = UIColor(red: 243/255, green: 243/255, blue: 243/255, alpha: 1)

        myTextField.delegate = self// must write this line
        
        setUpViews()// call func for constraint
    }
  //func for text limit
  func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
        let curruntCharachterCount = textField.text?.count ?? 0
        if range.length + range.location > curruntCharachterCount{
            return false
        }
        let newLength = curruntCharachterCount + string.count - range.length
        return newLength <= 1 // set max limit of numbers
    }
  
  func setUpViews() {
    //constraint setup
        view.addSubview(enterPinTextField)
    //textField constraint
        enterPinTextField.topAnchor.constraint(equalTo: view.topAnchor, constant: 30).isActive = true
        enterPinTextField.centerXAnchor.constraint(equalTo: mainScreenView.centerXAnchor).isActive = true
        enterPinTextField.widthAnchor.constraint(equalToConstant: 150).isActive = true
    	enterPinTextField.heightAnchor.constraint(equalToConstant: 50).isActive = true
  }
}