Composing two observable sources using one as a predicate in RxJava

Question

I have 2 observable sources where fetchProductList() returns Observable<Datasource> and other canInvite.execute() takes a value and returns a Single<Boolean>. I need to compose the stream to feed every emission from first source to the second in a way that I can return all the emission from fetchProductList() with the true value as a list. I tried to compose it this way but it looks a bit clunky, Any better/simpler ways to do it?

fetchProductList()
                    .map { dataSource -> dataSource.data }
                    .flatMap{ data ->
                        Observable.from(data.roles.map { role ->
                            canInvite.execute(role.key).map { canInvite ->
                                role to canInvite
                            }
                        })
                    }

                    .compose { it -> Single.merge(it) }
                    .filter { it -> it.second == true}
                    .map { it -> it.first }
                    .toList()
                    .subscribe {

score 2 · Accepted Answer · answered Aug 27 '19 at 10:36

From my point of view, this is a bit more clear solution:

fetchProductList()
    .map { dataSource -> dataSource.data }
    .flatMap { data ->
        Observable.fromIterable(data.roles)
            .flatMapMaybe { role ->
                canInvite.execute(role.key)
                    .flatMapMaybe { result ->
                        if (result) Maybe.just(role) else Maybe.empty()
                    }
            }
    }
    .toList()
    .subscribe { result -> println(result) }

Composing two observable sources using one as a predicate in RxJava

1 Answers1