Retrofit & RxJava multiple requests complete

Question

I need to do:

1. Request 2 lists of news from different websites
2. Combine results from requests
3. Sort items by date
4. Get 10 newest news
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Answer 1

Well it depends, as always. Do you need to process the returned values down the chain, or just save it?

In this implementation I use Single and Completable. You subscribe to the completable and you will get notified when both Singles finished.

@Test
public void name() throws Exception {
        TestScheduler testScheduler = new TestScheduler();
        Single request1 = Single.timer(1000, TimeUnit.MILLISECONDS, testScheduler)
                .doOnSuccess(aLong -> {
                    System.out.println("save to db.");
                });
        Single request2 = Single.timer(500, TimeUnit.MILLISECONDS, testScheduler)
                .doOnSuccess(aLong -> {
                    System.out.println("save to db.");
                });

        Completable completable = Single.zip(request1, request2, (aLong, aLong2) -> aLong).toCompletable();

        TestObserver test = completable.test();

        testScheduler.advanceTimeBy(1010, TimeUnit.MILLISECONDS);

        test.assertComplete();
}

You also can use flatMapCompletable instead of doOnSuccess

@Test
public void name() throws Exception {
    TestScheduler testScheduler = new TestScheduler();
    Completable request1 = Single.timer(1000, TimeUnit.MILLISECONDS, testScheduler)
            .flatMapCompletable(this::saveToDb);

    Completable request2 = Single.timer(500, TimeUnit.MILLISECONDS, testScheduler)
            .flatMapCompletable(this::saveToDb);

    // need to cheat here, becuase completeable does not provide zip
    Completable completable = Single.zip(request1.toSingle(() -> 1), request1.toSingle(() -> 1), (aLong, aLong2) -> aLong)
            .toCompletable();

    TestObserver test = completable.test();

    testScheduler.advanceTimeBy(1010, TimeUnit.MILLISECONDS);

    test.assertComplete();
}

private Completable saveToDb(long value) {
    return Completable.complete();
}