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

All pre-implemented final methods are thread-safe.

Override the protected onStart() to perform initialization when this ResourceSingleObserver 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() and onError() explicitly.

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

Like all other consumers, ResourceSingleObserver 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) and onError(Throwable) are not allowed to throw any unchecked exceptions.

Example

Disposable d =
    Single.just(1).delay(1, TimeUnit.SECONDS)
    .subscribeWith(new ResourceSingleObserver<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();
        }
    });
// ...
d.dispose();