CodePiece.swift

class AmountSettingViewModelSpec: QuickSpec {
    override func spec() {
        var viewModel: AmountSettingViewModel!
        beforeEach {
            viewModel = AmountSettingViewModel(amountText: Observable<String>.just("120"),
                                               submitButtonTap: Observable<Void>.just())
            
        }
        it("should be button ebanled") {
            let enable = try! viewModel.submitButtonEnable.toBlocking().single()
            expect(enable).to(beTrue())
        }
        it("should be ¥120") {
            let amount = try! viewModel.amount.toBlocking().single()
            expect(amount).to(equal(120))
        }
        context("¥0") {
            beforeEach {
                viewModel = AmountSettingViewModel(amountText: Observable<String>.just("0"),
                                                   submitButtonTap: Observable<Void>.just())
                
            }
            it("should be button disabled") {
                let enable = try! viewModel.submitButtonEnable.toBlocking().single()
                expect(enable).to(beFalse())
            }
            it("should be ¥0") {
                let amount = try! viewModel.amount.toBlocking().single()
                expect(amount).to(equal(0))
            }

        }
    }
}

struct AmountSettingViewModel {
    let submitButtonEnable: Observable<Bool>
    let amount: Observable<Int>
    
    init(amountText: Observable<String>, submitButtonTap: Observable<Void>) {
        amount = amountText.map { Int($0) ?? 0 }.shareReplayLatestWhileConnected()
        submitButtonEnable = amount.map { $0 > 0 }
    }
}

class AmountSettingViewController: UIViewController {
    @IBOutlet weak var textField: UITextField!
    @IBOutlet weak var submitButton: UIButton!
    
    lazy var viewModel: AmountSettingViewModel = {
        return AmountSettingViewModel(amountText: self.textField.rx.text,
                                      submitButtonTap: self.submitButton.rx.tap)
    }()
    private let disposeBag = DisposeBag()
    
    override func viewDidLoad() {
        super.viewDidLoad()

        viewModel.submitButtonEnable.bindTo(submitButton.rx.isEnabled)
            .addDisposableTo(disposeBag)
        viewModel.amount.subscribe(onNext: { [weak self] amount in
          //self?.present(viewController, animated: true, completion: nil)
        }).addDisposableTo(disposeBag)
    }
}