ViewController.swift

class ViewController: UIViewController {

    @IBOutlet weak var textField: UITextField!
    @IBOutlet weak var resultLabel: UILabel!
    var viewModel: ViewModel!
    let disposeBag = DisposeBag()
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    @IBAction func checkEvenNumber(sender: AnyObject) {
        
        viewModel = ViewModel()
        
        textField
            .rx_observe(String.self, "text")
            .bindTo(viewModel.numberVariable)
            .addDisposableTo(disposeBag)
        
        viewModel.isEvenObservable
            .subscribeNext {isEven in
                self.resultLabel.text = isEven
        }
            .addDisposableTo(disposeBag)
    }

}