Delegate Methods

// MARK: - UITextFieldDelegate
extension ViewController: UITextFieldDelegate {

    // return NO to disallow editing.
    func textFieldShouldBeginEditing(_ textField: UITextField) -> Bool {
        return true
    }

    // became first responder
    func textFieldDidBeginEditing(_ textField: UITextField) {
    }

    // return YES to allow editing to stop and to resign first responder status.
    // return NO to disallow the editing session to end
    func textFieldShouldEndEditing(_ textField: UITextField) -> Bool {
        return true
    }

    // if implemented, called in place of textFieldDidEndEditing: ?
    func textFieldDidEndEditing(_ textField: UITextField) {
    }

    // detect - keypress
    // return NO to not change text
    func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
        let word = textField.text ?? ""
        let char = string
        print("Default - shouldChangeCharactersIn: \(word) \(char)")
        return true
    }

    // called when 'clear' button pressed. return NO to ignore (no notifications)
    func textFieldShouldClear(_ textField: UITextField) -> Bool {
        return true
    }

    // called when 'return' key pressed. return NO to ignore.
    func textFieldShouldReturn(_ textField: UITextField) -> Bool {
        textField.endEditing(true) // resign first responder
        return true
    }
}

텍스트 변경 알림 받기

textField.addTarget(self, action: #selector(textFieldEditingChanged), for: .editingChanged)

@objc func textFieldEditingChanged(_ sender: UITextField) {
	print(sender.text!)
}