RxJava: How to convert List of objects to List of another objects

Question

I have the List of SourceObjects and I need to convert it to the List of ResultObjects.

I can fetch one object to another using method of ResultObject:

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Answer 1

As an extension to Noel great answer. Let's say transformation also depends on some server data that might change during subscription. In that case use flatMap + scan.

As a result when id list changes, transformations will restart anew. And when server data changes related to a specific id, single item will be retransformed as well.

fun getFarmsWithGroves(): Observable> {

        return subscribeForIds() //may change during subscription
                .switchMap { idList: Set ->

                    Observable.fromIterable(idList)
                            .flatMap { id: String -> transformId(id) } //may change during subscription
                            .scan(emptyList()) { collector: List, candidate: FarmWithGroves ->
                                updateList(collector, candidate)
                            }
                }
    }