What is the difference between Rx.Observable subscribe and forEach

Question

After creating an Observable like so

var source = Rx.Observable.create(function(observer) {...});

What is the difference between su

Answer 1

I just review the latest code available, technically the code of foreach is actually calling subscribe in RxScala, RxJS, and RxJava. It doesn't seems a big different. They now have a return type allowing user to have an way for stopping a subscription or similar.

When I work on the RxJava earlier version, the subscribe has a subscription return, and forEach is just a void. Which you may see some different answer due to the changes.

/**
 * Subscribes to the [[Observable]] and receives notifications for each element.
 *
 * Alias to `subscribe(T => Unit)`.
 *
 * $noDefaultScheduler
 *  
 * @param onNext function to execute for each item.
 * @throws java.lang.IllegalArgumentException if `onNext` is null
 * @throws rx.exceptions.OnErrorNotImplementedException if the [[Observable]] tries to call `onError`
 * @since 0.19
 * @see ReactiveX operators documentation: Subscribe
 */
def foreach(onNext: T => Unit): Unit = {
    asJavaObservable.subscribe(onNext)
 }

def subscribe(onNext: T => Unit): Subscription = {
    asJavaObservable.subscribe(scalaFunction1ProducingUnitToAction1(onNext))
}

/**
 *  Subscribes an o to the observable sequence.
 *  @param {Mixed} [oOrOnNext] The object that is to receive notifications or an action to invoke for each element in the observable sequence.
 *  @param {Function} [onError] Action to invoke upon exceptional termination of the observable sequence.
 *  @param {Function} [onCompleted] Action to invoke upon graceful termination of the observable sequence.
 *  @returns {Disposable} A disposable handling the subscriptions and unsubscriptions.
 */
observableProto.subscribe = observableProto.forEach = function (oOrOnNext, onError, onCompleted) {
  return this._subscribe(typeof oOrOnNext === 'object' ?
    oOrOnNext :
    observerCreate(oOrOnNext, onError, onCompleted));
};

/**
 * Subscribes to the {@link Observable} and receives notifications for each element.
 * 

 * Alias to {@link #subscribe(Action1)}
 * 

 *  
Scheduler:
 *  
{@code forEach} does not operate by default on a particular {@link Scheduler}.
 * 
 * 
 * @param onNext
 *            {@link Action1} to execute for each item.
 * @throws IllegalArgumentException
 *             if {@code onNext} is null
 * @throws OnErrorNotImplementedException
 *             if the Observable calls {@code onError}
 * @see ReactiveX operators documentation: Subscribe
 */
public final void forEach(final Action1 onNext) {
    subscribe(onNext);
}

public final Disposable forEach(Consumer onNext) {
    return subscribe(onNext);
}