How to use RxJava2 combineLatest with a list of observables in Kotlin

Question

I know how to do this in RxJava 2.

And I know how RxKotlin helps with similar issues.

But it seems that RxKotlin.Observables doesn't have this helper function for the list overload and I cannot figure it out. How would you do this?

It's an extension function on `Iterable>`. Do `listOfObservables.combineLatest { ... }` — marstran, Dec 23 '17 at 16:57

marstran · Accepted Answer · 2017-12-26T22:41:41.343

6

Most static functions in RxJava are extension functions in RxKotlin. This particular function is an extension on Iterable<Observable<T>>. You can call it like this:

listOfObservables.combineLatest { ... }

edited Dec 26 '17 at 22:41

answered Dec 25 '17 at 19:03

marstran

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score 6 · Answer 2 · answered Dec 12 '18 at 19:50

for RxJava 2 this could be done in this way

    val list = Arrays.asList(
            remoteRepository.getHospitals(),
            remoteRepository.getQuestionCategories(),
            remoteRepository.getQuestions(),

    )


    return Observable.combineLatest(list) {

        val hospitals = it[0] as List<Hospital>

        val questionCategories = it[1] as List<QuestionCategory>
        val questions = it[2] as List<Question>


        localRepository.insertHospitals(hospitals)
        localRepository.insertQuestionCategories(questionCategories)
        localRepository.insertQuestions(questions)


        if (hospitals.isNotEmpty())
            Constants.STATUS_OK
        else
            Constants.STATUS_ERROR

    }

score 1 · Answer 3 · edited Feb 16 '18 at 14:14

val list = Arrays.asList(Observable.just(1), Observable.just("2"))
Observable.combineLatest(list, object : FuncN<String>() {
    fun call(vararg args: Any): String {
        var concat = ""
        for (value in args) {
            if (value is Int) {
                concat += value
            } else if (value is String) {
                concat += value
            }
        }
        return concat
    }
})

Observable.just(1), Observable.just("2") can be replaced with list of observable and login inside call fun will also changed as per requirements.

How to use RxJava2 combineLatest with a list of observables in Kotlin

3 Answers3