Simplify a method which returns a RxJava Single type

Question

I return a RxJava Single type as you see bellow :

private fun getSpeciesWrapper(
    character: Character, getSpecieUseCase: GetSpecieUseCase, getPlanetUseCase: GetPlanetUseCase,
): Single<List<SpecieWrapper>> {
    var name: String? = null
    var language: String? = null
    return Flowable.fromIterable(character.specieUrls)
            .flatMapSingle { specieUrl -> getSpecieUseCase(specieUrl) }
            .flatMapSingle { specie ->
                name = specie.name
                language = specie.language
                getPlanetUseCase(specie.homeWorld)
            }.map { planet ->
                SpecieWrapper(name, language, planet.population)
            }.toList()
}

As you see I have defined name and language variables in order to use them in the map section to create a list of Specie wrapper.

Is there any solution in RxJava2 that I could simplify the Single type by removing these local variables (name and language) ?

Answer 1

You can simply nest the map call inside of the flatMapSingle call:

private fun getSpeciesWrapper(
    character: Character, getSpecieUseCase: GetSpecieUseCase, getPlanetUseCase: GetPlanetUseCase,
): Single<List<SpecieWrapper>> {
    return Flowable.fromIterable(character.specieUrls)
            .flatMapSingle { specieUrl -> getSpecieUseCase(specieUrl) }
            .flatMapSingle { specie -> getPlanetUseCase(specie.homeWorld)
                .map { planet ->
                    SpecieWrapper(specie.name, specie.language, planet.population)
                }
            }.toList()
}