CODEWITHSUNDEEP
androidrx-javarx-java2
MBH
MBH

Reputation: 16639

Execute 2 observables sequentially and get the result at once - RxJava 2

I have this function: 

public static class CombinedResult<T, R> {
    T t;
    R r;

    public CombinedResult(T t, R r) {
        this.t = t;
        this.r = r;
    }

    public T getObject1() {
        return t;
    }

    public void setObject1(T t) {
        this.t = t;
    }

    public R getObject2() {
        return r;
    }

    public void setObject2(R r) {
        this.r = r;
    }

}

public static <A, B> Observable<CombinedResult<A, B>> combineObservablesParallel(Observable<A>
    return Observable.zip(observable1, observable2, new BiFunction<A, B, CombinedResult<A, B>>() {
        @Override
        public CombinedResult<A, B> apply(A a, B b) throws Exception {
            return new CombinedResult<>(a,b);
        }
    });
}

It combine 2 observables and return 1 Observable, which will get the result of both observables into CombinedResult object, The problem here is zip function combine the observables on Paralllel.

I want something same as zip that executes the observable sequentially and return the result in BiFunction or something like this.

what can be the solution ?

Upvotes: 3

Views: 3357

Answers (1)

R. Zag&#243;rski
R. Zag&#243;rski

Reputation: 20268

Use flatMap operator on observable1 combined with observable2 and zip operator:

RxJava 1:

return observable1
                .flatMap(new Func1<A, Observable<CombinedResult<A, B>>>() {
                    @Override
                    public Observable<CombinedResult<A, B>> call(A a) {
                        return Observable.just(a).zipWith(observable2, new Func2<A, B, CombinedResult<A, B>>() {
                            @Override
                            public CombinedResult<A, B> call(A a, B b) {
                                return new CombinedResult<>(a, b);
                            }
                        });
                    }
                });

RxJava 2:

return observable1.flatMap(new Function<A, ObservableSource<CombinedResult<A,B>>>() {
    @Override
    public ObservableSource<CombinedResult<A,B>> apply(A a) throws Exception {
        return Observable.just(a).zipWith(observable2, new BiFunction<A, B, CombinedResult<A, B>>() {
            @Override
            public CombinedResult<A, B> apply(A a, B b) throws Exception {
                return new CombinedResult<>(a,b);
            }
        });
    }
});

RxJava 2 Lambda: 

return observable1.flatMap(a -> Observable.just(a).zipWith(observable2, CombinedResult::new));

Upvotes: 4

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