Change Data type in the RxJava2 chain

Question

I am new to RxJava2 and its methods. I need to change the data type which is emitted from an Observable.

Say, I have a data class like below.

data class SomeClass (val type: String)

An API returns ArrayList<SomeClass>, this works fine on the current implementation using RxJava2 and RxAndroid.

apiService.getPrice(code)
            .subscribeOn(Schedulers.io())
            .observeOn(AndroidSchedulers.mainThread())
            .subscribe(singleObserver)

I have to change/transform the data from ArrayList<SomeClass> to HashMap<someClassObject.type, ArrayList<SomeClass>>. I am trying operators to make this happen, but no operator will allow changing the datatype being observed.

Transform based on:

Consumer<ArrayList<SomeClass>> { response ->
                    val mapped = HashMap<String, ArrayList<SomeClass>>()
                    response.forEach { someClassObj ->
                        val type = someClassObj.type!!
                        if (mapped.containsKey(type)) {
                            mapped[district]?.add(someClassObj)

                        } else {
                            val list = ArrayList<SomeClass>()
                            list.add(someClassObj)
                            mapped[type] = list
                        }
                    }
                }

I am thinking to use two different observables, in which Observable data #2 is based on the response of Observable data #1 (ArrayList<SomeClass>). But, I am not sure if this works. Any better or efficient way to achieve this?

Answer 1

Try map:

apiService.getPrice(code)
        .map { response ->
            val mapped = HashMap<String, ArrayList<SomeClass>>()
            response.forEach { someClassObj ->
                val type = someClassObj.type!!
                if (mapped.containsKey(type)) {
                    mapped[district]?.add(someClassObj)
                } else {
                    val list = ArrayList<SomeClass>()
                    list.add(someClassObj)
                    mapped[type] = list
                }
            }
            mapped
        }
        .subscribeOn(Schedulers.io())
        .observeOn(AndroidSchedulers.mainThread())
        .subscribe(singleObserver);