subscribeOn

Ensures that the subscription to the source observable happens on the provided scheduler.

The source must emit on this same scheduler (see the first warning below); this operator moves only the subscription, not the emission thread. It is useful to consume (via observeOn) an Observable that emits from a thread different from the consumer's.

Example:

// sourceScheduler: the scheduler the subject emits on
// consumerScheduler: the scheduler the consumer wants its values on
val subject = Observables.publishSubject<Int>()

consumerScheduler.execute {
    subject.asObservable()
        .subscribeOn(sourceScheduler)   // subscribe to `subject` on the scheduler it emits from
        .observeOn(consumerScheduler)   // hop the emissions over to the consumer
        .take(1)
        .map { it * 10 }
        .subscribe { println(it) }      // must run on consumerScheduler, see the second warning
}

sourceScheduler.execute {
    subject.onNext(1)
}

Warning. This method is intended for observables that emit from the same scheduler as the one provided here. Calling this method on an Observable that emits from a different scheduler will cause race conditions.

You can subscribe to this Observable directly and you will receive onNext and onComplete from the source scheduler (which must be the same as the provided scheduler) and you can dispose from any thread.

Warning. You can't chain any operator to the returned Observable other than observeOn with the scheduler on which the consumer runs. After doing that you can chain any other operator, as long as it also works from that same scheduler.