let username = usernameTextField
            .rx
            .text
            .orEmpty
            .map({ (text) -> Bool in
                text.count > 5
            })


        let password = passwordTextField
            .rx
            .text
            .orEmpty
            .map({ (text) -> Bool in
                text.count > 5
            })

        Observable.combineLatest(username, password) { (username, password)  in
            username && password
            }.bind(to: loginButton.rx.isEnabled)
            .disposed(by: disposeBag)