How to track the state of a textField?

Question

Swift

How to understand that the user has started typing text in a textField? By type willSet and didSet for a variable

Answer 1

UITextField inherits from UIControl, which means you can subscribe to its controlEvents. Example:

override func viewDidLoad() {
        super.viewDidLoad()
        textField.addTarget(self, action: #selector(editingBegan(_:)), for: .editingDidBegin)
        textField.addTarget(self, action: #selector(editingChanged(_:)), for: .editingChanged)
        textField.addTarget(self, action: #selector(editingEnded(_:)), for: .editingDidEnd)
    }

    @objc func editingBegan(_ textField: UITextField) {
        //пользователь попал в поле, но еще ничего не ввел
    }

    @objc func editingChanged(_ textField: UITextField) {
        //текст изменился
    }

    @objc func editingEnded(_ textField: UITextField) {
        //ввод окончен, к примеру нажали "return" на клавиатуре
    }

Answer 2

It is easier to write not just a function, but to make an @IBAction, for which, through the StoryBoard, specify after which event it should work:
- EditingDidBegin,
- EditingDidEnd,
etc... - which one is needed.