Which is right way to map few server models into one domains?

Question

My server api looks like this:

data class ArticleDTO(val id: Int, val title: String, val typeId: Int)
data class Type(val id: Int, val name: String) 

interface API {
    fun getArticles(): Single<List<ArticleDTO>>
    fun getTypes(): Single<List<Type>>
}

And I have one model which I use in UI:

data class Article(val title: String, val typeName: String)

I created map method:

fun ArticleDTO.toArticle(type: Type) = Article(this.title, typeName = type.name)

And in the repository class I did this:

fun getArticles() =
    Observables.combineLatest(api.getArticles().toObservable(), api.getTypes().toObservable())
        .flatMap {
            Observable.just(it.first.map { articleDTO ->
                articleDTO
                    .toArticle(it.second.find { type -> type.id == articleDTO.typeId }!!)
            })
        }

Is there a way to do it better?

And what if my api will looks like this:

interface API {
    fun getArticles(): Single<List<ArticleDTO>>
    fun getTypes(typeId: Int): Single<Type>
}

Answer 1

You can get rid of flatMap and Observable.just

fun getArticles() = Observables.combineLatest(api.getArticles().toObservable(), api.getTypes().toObservable())
        .map { (dtos, types) ->
            dtos.map { articleDTO ->
                articleDTO
                    .toArticle(types.find { type -> type.id == articleDTO.typeId }!!)
            }
        }