Mix and match RxJava subscription threads

Question

Is it possible to mix and match scheduler threads in RxJava. Basically I want to do something like the following on Android.

uiObservable
    .switchMap(o -> return anotherUIObservable)
    .subscribeOn(AndroidSchedulers.mainThread())
    .switchMap(o -> return networkObservable)
    .subscribeOn(Schedulers.newThread())
    .observeOn(AndroidSchedulers.mainThread())
    .subscribe(result -> doSomething(result))

Is that possible within the same subscription ?

score 3 · Accepted Answer · answered Sep 07 '15 at 20:22

Yes it's possible and really easy after you have fully understand the logic. But you probably confuse a bit observeOn() and subscribeOn() operators :)

uiObservable
    .switchMap(o -> return anotherUIObservable)
    .subscribeOn(AndroidSchedulers.mainThread())  // means that the uiObservable and the switchMap above will run on the mainThread.

    .switchMap(o -> return networkObservable) //this will also run on the main thread

    .subscribeOn(Schedulers.newThread()) // this does nothing as the above subscribeOn will overwrite this

    .observeOn(AndroidSchedulers.mainThread()) // this means that the next operators (here only the subscribe will run on the mainThread
    .subscribe(result -> doSomething(result))

Maybe this is what you want:

uiObservable
    .switchMap(o -> return anotherUIObservable)
    .subscribeOn(AndroidSchedulers.mainThread()) // run the above on the main thread

    .observeOn(Schedulers.newThread())
    .switchMap(o -> return networkObservable) // run this on a new thread

    .observeOn(AndroidSchedulers.mainThread()) // run the subscribe on the mainThread
    .subscribe(result -> doSomething(result))

Bonus: I have written a post about these operators, hope it helps

Thanks !! I now have a bunch of follow up questions that I will be putting forth as and when I get the time. — Saad Farooq, Sep 09 '15 at 01:07

Mix and match RxJava subscription threads

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