ReactiveSwift action observeResult doesn't return failure like it should be

Question

nowadays I am interested in ReactiveSwift and trying to add it for networking actions of the project. But there are some problems about action return type with observeResult method.

view model:

final class TestViewModel: ViewModel {

    var getListAction: Action<Void, Void, APIError>!

    var arr = NSMutableArray()

    override init() {

        super.init()

        self.getListBuild()

    }

    func getListBuild() {

        getListAction = Action<Void, Void, APIError> { _ in
            let signalProducer = SignalProducer<Void, APIError> { observer, disposable in
                self.getList(observer)
            }
            return signalProducer
        }

        getListAction.apply().start()
    }


    func getList(_ observer: Observer<Void, APIError>) {

        Network<UserDetailInfo>().requestList(router: RegistrationRouter(endpoint:.Login())).take(during: lifetime).startWithResult { (result) in
            switch result {
            case let .success(value):
                self.arr = value as! NSMutableArray
                print("success")
                observer.sendCompleted()
            case let .failure(error):
                print("abort: \(String(describing: error.message))")
                observer.send(error: error)
            }
        }
    }
}

and from the controller I have tried to manage it like this :

final class ViewController: View {

    var viewModel: TestViewModel?

    func bindViewModel() {

        self.viewModel = TestViewModel()

        self.viewModel?.getListAction.events.take(during: lifetime).observeResult { (result) in
            switch result {
            case .success(_):
                print("success")
                print(self.viewModel?.arr.count as Any)
                break
            case let .failure(error):
                print(error.localizedDescription);
                break
            }
        }
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        self.bindViewModel()
    }
}

Despite of returning failure from getList method in viewModel, situation like this :

method returned success but it is not. It should be failure. Please let me learn what the problem is about this subject.

Answer 1

The event stream you observe will never return a failure. See its documentation:

/// A signal of all events generated from applications of the Action.
///
/// In other words, this will send every `Event` from every signal generated
/// by each SignalProducer returned from apply() except `ActionError.disabled`.
public let events: Signal<Event<Output, Error>, NoError>

To observe successful values, you would want to subscribe to the values and use observeValues:

self.viewModel?.getListAction
   .values
   .take(during: lifetime)
   .observeValues { [weak self] value in
      // always successful
   }

If you want to observe errors, you can subscribe to errors and use observeValues.

self.viewModel?.getListAction
   .errors
   .take(during: lifetime)
   .observeValues { [weak self] error in
      // error event
   }