An abstract Observer that allows asynchronous cancellation of its subscription and associated resources.

All pre-implemented final methods are thread-safe.

To release the associated resources, one has to call dispose() in onError() and onComplete() explicitly.

Use add(Disposable) to associate resources (as Disposables) with this ResourceObserver that will be cleaned up when dispose() is called. Removing previously associated resources is not possible but one can create a CompositeDisposable, associate it with this ResourceObserver and then add/remove resources to/from the CompositeDisposable freely.

Use the dispose() to dispose the sequence from within an onNext implementation.

Like all other consumers, ResourceObserver can be subscribed only once. Any subsequent attempt to subscribe it to a new source will yield an IllegalStateException with message "It is not allowed to subscribe with a(n) <class name> multiple times.".

Implementation of onStart(), onNext(Object), onError(Throwable) and onComplete() are not allowed to throw any unchecked exceptions. If for some reason this can't be avoided, use io.reactivex.rxjava3.core.Observable#safeSubscribe(io.reactivex.rxjava3.core.Observer) instead of the standard subscribe() method.

Example

Disposable d =
    Observable.range(1, 5)
    .subscribeWith(new ResourceObserver<Integer>() {
        @Override public void onStart() {
            add(Schedulers.single()
                .scheduleDirect(() -> System.out.println("Time!"),
                    2, TimeUnit.SECONDS));
            request(1);
        }
        @Override public void onNext(Integer t) {
            if (t == 3) {
                dispose();
            }
            System.out.println(t);
        }
        @Override public void onError(Throwable t) {
            t.printStackTrace();
            dispose();
        }
        @Override public void onComplete() {
            System.out.println("Done!");
            dispose();
        }
    });
// ...
d.dispose();