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

All pre-implemented final methods are thread-safe.

Note that onSuccess(Object), onError(Throwable) and onComplete() are exclusive to each other, unlike a regular Observer, and onComplete() is never called after an onSuccess().

Override the protected onStart() to perform initialization when this ResourceMaybeObserver is subscribed to a source.

Use the public dispose() method to dispose the sequence externally and release all resources.

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

Use add(Disposable) to associate resources (as Disposables) with this ResourceMaybeObserver 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 ResourceMaybeObserver and then add/remove resources to/from the CompositeDisposable freely.

Like all other consumers, ResourceMaybeObserver 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(), onSuccess(Object), onError(Throwable) and onComplete() are not allowed to throw any unchecked exceptions.

Example

Disposable d =
    Maybe.just(1).delay(1, TimeUnit.SECONDS)
    .subscribeWith(new ResourceMaybeObserver<Integer>() {
        @Override public void onStart() {
            add(Schedulers.single()
                .scheduleDirect(() -> System.out.println("Time!"),
                    2, TimeUnit.SECONDS));
        }
        @Override public void onSuccess(Integer t) {
            System.out.println(t);
            dispose();
        }
        @Override public void onError(Throwable t) {
            t.printStackTrace();
            dispose();
        }
        @Override public void onComplete() {
            System.out.println("Done!");
            dispose();
        }
    });
// ...
d.dispose();