merge rx observable

worksheet.scala

import rx.lang.scala._
import rx.lang.scala.subjects.ReplaySubject

import scala.concurrent.Promise
import scala.concurrent.ExecutionContext.Implicits.global

val r = ReplaySubject[Int]()

r.onNext(1)
r.onNext(2)
r.onNext(3)

val promise = Promise[List[Int]]()

val zz = Observable.defer(Observable[Int] { observer =>
  r.doOnNext(observer.onNext).subscribe()
  observer.onCompleted()
})
  .subscribeOn(schedulers.NewThreadScheduler()).toList
  .subscribe(l => promise.success(l.reverse))

promise.future map println

//I wish it prints [1 2 3]

r.onNext(4)