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class ViewController: UIViewController {

    @IBOutlet weak var loginTextField: UITextField?
    @IBOutlet weak var passwordTextField: UITextField?
    @IBOutlet weak var loginButton: UIButton?
    
    private let disposeBag = DisposeBag()
    private let viewModel = ViewModel()
    
    override func viewDidLoad() {
        super.viewDidLoad()
    
        loginButton?.isEnabled = false
        
        guard let loginTextField = loginTextField,
            let passwordTextField = passwordTextField,
            let loginButton = loginButton else {
                return
        }

//send the entered login value to the model
   loginTextField.rx.text.orEmpty
            .distinctUntilChanged()
            .bind(to: viewModel.loginInputPublisher)
            .disposed(by: disposeBag)

//send the entered password value to the model
      passwordTextField.rx.text.orEmpty
            .distinctUntilChanged()
            .bind(to: viewModel.passworInputdPublisher)
            .disposed(by: disposeBag)

//subscribe to loginEnabledDriver and set the isEnabled of the button
 viewModel.loginEnabledDriver
            .drive(loginButton.rx.isEnabled)
            .disposed(by: disposeBag)
    }



    class ViewModel {

    let loginInputPublisher: PublishSubject<String> = PublishSubject()
    let passworInputdPublisher: PublishSubject<String> = PublishSubject()
    
    let loginEnabledDriver: Driver<Bool>
    
    init() {
        loginEnabledDriver = Observable.combineLatest(loginInputPublisher, passworInputdPublisher) { (login, password) in
            return login.isLoginValid && password.isPasswordValid
            }
            .asDriver(onErrorJustReturn: false)
    }
}