RxSwift call a simple function on a Scheduler

Question

I have a simple non-reactive function that I'd like to run on a SerialDispatchQueueScheduler. The method doesn't return anything neither I require it to emit any events but it has to be run on a scheduler

func deleteDataOf(_ personId: Int, on scheduler: SerialDispatchQueueScheduler) {
    //Run the method body on scheduler
    try? removeItem(at: getDirectoryURL(personId: personId))
}

Answer 1

The simplest solution is to put your side effect in a .do(onNext:), or .subscribe(onNext:) operator that is invoked on the scheduler in question. That way it's part of the observable chain.

The next simplest is to schedule the operation on the scheduler:

func deleteDataOf(_ personId: Int, on scheduler: SchedulerType) -> Disposable {
    scheduler.schedule(()) {
        try? removeItem(at: getDirectoryURL(personId: personId))
        return Disposables.create()
    }
}

Note that it returns a Disposable for possible cancelation.

I notice that your side effect throws, which implies to me that you are potentially interested in errors. Maybe a Completable would be a better idea, but then you would have to subscribe to the result.

Something like this:

func deleteDataOf(_ personId: Int) -> Completable {
    Completable.deferred {
        do {
            try removeItem(at: getDirectoryURL(personId: personId))
            return .empty()
        }
        catch {
            return .error(error)
        }
    }
}

func deleteDataOf(_ personId: Int, on scheduler: SchedulerType) {
    _ = deleteDataOf(personId)
        .subscribeOn(scheduler)
        .subscribe(onError: { print("there was an error", $0) })
}