Allowing single digit in UITextField in iOS

Question

I have a Verification ViewController, I get 4 digit verification code by SMS and I need to enter those code to login, I have created the ViewController

Answer 1

Swift 4

when you input a number from the pin code into a text field, you should let a number be shown and then the next text field will become the first responder, so change the first responder after the code was in the text view

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    guard let textField = textField as? PinCodeTextField else { return true }

    if string == "" {// when the backward clicked, let it go :)
        return true
    }

    // when textfield is not empty, well, next number
    if textField.pinCode.count == textField.maxCount {
        becomeFirstResponder(after: textField)
        return false
    }

    if string.count > textField.maxCharacterCount {// the max character count should be 1
        return false
    }
    return true
}
// now the text field has been filled with a number
func textFieldCotentDidChange(_ textField: UITextField) {
    print("didchange")
    guard let textField = textField as? PinCodeTextField else { return }
    if textField.pinCode.count == 0 {
        becomeFirstResponder(before: textField)
    }

    // when textfield has been filled, ok! next!
    if textField.pinCode.count == textField.maxCharacterCount {
        becomeFirstResponder(after: textField)
    }
}

for more details and the simple demo, see this link