In My repository, I have two API calls that should be done sequentially.

1. First API call returns Completable -> If this API call fails, we should not proceed further, if it succeeds we should continue with the second API call
2. Second API call returns Single -> If this API call fails, we should NOT throw an error and we can still continue

How can I achieve this?

What I am doing now is using separate calls from repo.

Repository:

override fun activate(id: String): Completable {
    return api1.post(Body(id = id))
        .subscribeOn(schedulerProvider.io())
}

override fun fetchAd(id: String): Single<SummaryAd> {
    return api2.getAd(adId)
        .subscribeOn(schedulerProvider.io())
        .map { it.toSummaryAd() }
}

ViewModel:

private fun activate(id: String) {
    repository.activate(id)
        .subscribeOn(schedulerProvider.io())
        .observeOn(schedulerProvider.ui())
        .subscribe(
            { // if it is successful, let's continue
                fetchAd(id)
            },
            { // otherwise fail
                _state.value = State.ErrorActivation
            }
        ).also { compositeDisposable.add(it) }
}

private fun fetchAd(id: String) {
    repo.fetchAd(id)
        .subscribeOn(schedulerProvider.io())
        .observeOn(schedulerProvider.ui())
        .subscribe(
            { // success
                _state.value = State.ActivationSuccess(it)
            },
            {
                // even though the call has failed, the activation is succeeded, so we still can proceed but with empty data
                _state.value = State.ActivationSuccess(SummaryAd())
            }
        ).also { compositeDisposable.add(it) }
}

Basically what I want ultimately is to have a single function in my viewModel and let the repository sequentially call them and only throw error If the first API call failed.

CodePudding user response：

Use andThen

activate(id)
.andThen(
    fetchAd(id)
    .onErrorReturnItem(SummaryAd())
)

CodePudding user response：

This is roughly what you need, depending on your implementation of _state you might also not need to set its value on UI thread.

 compositeDisposable.add(
            repository.activate(id)
                .subscribeOn(schedulerProvider.io())
                .andThen{
                    repo.fetchAd(id)
                        .subscribeOn(Schedulers.io())
                        .onErrorReturnItem { SummaryAd() }
                }
                .observeOn(schedulerProvider.ui())
                .subscribe(
                    {
                        _state.value = State.ActivationSuccess(it)
                    },
                    {
                        // this will be executed only, in case of activate request failure, as fetch add can never fail due to one rrorReturn
                        _state.value = State.ErrorActivation
                    }
                )
        )