Prevent disposal of PublishSubject (RxSwift) - ios

Question

I'm struggling with specific use-case incorporating RxSwift's PublishSubject.
For sake of simplicity unimportant details were omitted.
There is a MVVM setup. In VC I have a UIButton, on tap of which a network call should dispatch. In ViewModel I have a buttonDidTapSubject: PublishSubject<Void>.
class ViewModel {
let disposeBag = DisposeBag()
let buttonDidTapSubject = PublishSubject<Void>()
let service: Service
typealias Credentials = (String, String)
var credentials: Observable<Credentials> {
return Observable.just(("testEmail", "testPassword"))
}
init(_ service: Service) {
self.service = service
buttonDidTapSubject
.withLatestFrom(credentials)
.flatMap(service.login) // login method has signature func login(_ creds: Credentials) -> Observable<User>
.subscribe(onNext: { user in print("Logged in \(user)") },
onError: { error in print("Received error") })
.disposed(by: disposeBag)
}
}
class ViewController: UIViewController {
let viewModel: ViewModel
let button = UIButton()
init(_ viewModel: ViewModel) {
self.viewModel = viewModel
}
}
In controller's viewDidLoad I make a binding:
override func viewDidLoad() {
button.rx.tap.asObservable()
.subscribe(viewModel.buttonDidTapSubject)
.disposed(by: disposeBag)
}
The problem is, since network request can fail and Observable that is returned from login(_:) method will produce an error, the whole subscription to buttonDidTapSubject in ViewModel will be disposed. And all other taps on a button will not trigger sequence to login in ViewModel.
Is there any way to avoid this kind of behavior?

Answer 1

You can use retry to prevent finishing the subcription. If you only want to retry in specific cases or errors you can also use retryWhen operator
In the view model:
lazy var retrySubject: Observable<Void> = {
return viewModel.buttonDidTapSubject
.retryWhen { error in
if (error == .networkError){ //check here your error
return .just(Void())
} else {
return .never() // Do not retry
}
}
}()
In the view controller I would have done it in another way:
override func viewDidLoad() {
super.viewDidLoad()
button.rx.tap.asObservable()
.flatMap { [weak self] _ in
return self?.viewModel.retrySubject
}
.subscribe(onNext: {
//do whatever
})
.disposed(by: disposeBag)
}

Answer 2

Not sure if still relevant - Use PublishRelay ( although it is RxCocoa )