What main difference textFieldDidChange and shouldChangeCharactersIn method, the delegate of UITextFieldDelegate?

Question

Can someone explain about when to use and how difference of them ?.

Answer 1

In Simple words textDidChange occurs when any text is typed in Textfield and you want to get text typed on TextField to check for validation or anything...

func textDidChange(_ textField: UITextField) {
        guard let email = emailTextField.text, !email.isEmpty, email.isValidEmail() else {
            //Write your code here...
            return }
        guard let password = passwordTextField.text, !password.isEmpty else {
            //Write your code here..
            return }
        //Write your success code. 
    }

And shouldChangeCharactersIn occurs event before any typed key is about to print in Textfield. So that you can varify that key and allow or restrict that key. Eg: If user enter space in Password Textfield you can restrict that key and space will never is printed in Textfield.

In below code I am restricting space(" ") key in My Textfields.

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
           if range.location == 0 && string == " " {
               return false
           }
           return true
       }