example.kt

import io.reactivex.Observable
import io.reactivex.schedulers.Schedulers

/*
What is blockingSubscribe() doing?

1. processing items on computation thread; not blocking main thread
2. processing items on computation thread; blocking main thread until terminal event
3. processing items on main thread; but not actually blocking main thread
4. processing items on main thread and blocking main thread until terminal event
 */

fun test() {
    println("Starting on: " + Thread.currentThread().name)

    Observable.just(1, 2, 3)
            .doOnSubscribe { println("Subscribing on thread: " + Thread.currentThread().name) }
            .subscribeOn(Schedulers.io())
            .doOnNext { println("Observing stream on thread: " + Thread.currentThread().name) }
            .observeOn(Schedulers.computation())
            .doOnNext { println("Jumped to thread: " + Thread.currentThread().name) }
            .blockingSubscribe { println("onNext, on thread: " + Thread.currentThread().name) }

    println("Ending on: " + Thread.currentThread().name)
}


/*
Answer:

#4, 
Not only is it blocking main thread (which I knew);
it's also processing items on the main thread, despite the observeOn() call.

Starting on: main
Subscribing on thread: RxCachedThreadScheduler-1
Observing stream on thread: RxCachedThreadScheduler-1
Observing stream on thread: RxCachedThreadScheduler-1
Observing stream on thread: RxCachedThreadScheduler-1
Jumped to thread: RxComputationThreadPool-1
Jumped to thread: RxComputationThreadPool-1
Jumped to thread: RxComputationThreadPool-1
onNext, on thread: main
onNext, on thread: main
onNext, on thread: main
Ending on: main
 */