RxJava - fetch every item on the list

Question

I have a method that returns an Observable>, which are ids of some Items. I\'d like to go through this list and download every Item

Answer 1

For Kotlin

 Observable
        .fromIterable(listOfChallenges) // list of challenges which contain challenge ID
        .flatMap { eachChallenge ->
            getChallengeDetail(eachChallenge.challengeUid!!) // fetch details of each challenge
        }
        .toList() // map to list
        .subscribe({ listOfEachChallengesDetail ->

        }, {
            // error
        })