Unused unsubscribe method on CompletableUseCase

[katien]

It looks like we're just creating an empty disposable in this class and disposing of it in unsubscribe without ever changing its value. In the SingleUseCase class, we pass an observer into the execute method and capture a reference to the subscription by subscribing inside of thhat method. I would have expected the same to happen in this class, or if the idea is that we subscribe manually from our presenter, shouldn't we also unsubscribe manually and remove this unsubscribe method altogether?

abstract class CompletableUseCase<in Params> protected constructor(
        private val threadExecutor: ThreadExecutor,
        private val postExecutionThread: PostExecutionThread) {
    // Here we initialize subscription as an empty disposable
    private val subscription = Disposables.empty()
    protected abstract fun buildUseCaseObservable(params: Params): Completable

    // I would have expected an observer to be passed into execute so that we can
    // subscribe in this method and obtain a reference to the subscription 
    fun execute(params: Params): Completable {
        return this.buildUseCaseObservable(params)
                .subscribeOn(Schedulers.from(threadExecutor))
                .observeOn(postExecutionThread.scheduler)
    }

    // Now we unsubscribe from our empty disposable
    fun unsubscribe() {
        if (!subscription.isDisposed) {
            subscription.dispose()
        }
    }
}

[ghost]

Any example for CompletableUseCase?

[qwertyfinger]

@DevKate In this case it's most probably a mistake.
I think CompletableUseCase should either hold the exact same logic as SingleUseCase:

fun execute(
        completableObserver: DisposableCompletableObserver, 
        params: Params
) {
        disposables.add(
            buildUseCaseObservable(params)
                .subscribeOn(Schedulers.from(threadExecutor))
                .observeOn(postExecutionThread.scheduler)
                .subscribeWith(completableObserver)
        )
    }

or return a Completable from execute() function and be stripped of subscription variable along with unsubcribe() function.
But in this case it's better to also have the same logic in SingleUseCase.

The choice between these two depends on whether you need to have access to a cold Observable in your Presenters (e.g. to combine them or apply some additional logic). I prefer using the latter in any case.
See this thread for more information.

[qwertyfinger]

@852dev Example usage? Saving some data to the database, for example. Anything where we don't need any actual data passed back to us, only the success/error status.