Subscriber

The subscriber represents the end-user. It receives the data at the very end of the stream and acts on it. The action may include updating a user interface, pushing it to another component, or transforming it in any way.

The interface of the subscribers contains four different callbacks, each of which represents a message of some type from the publisher or the subscriber itself:

• onSubscribe: The onSubscribe method is invoked as soon as the subscriber has a valid subscription. Generally, this is used to kick-start the delivery of items from the publisher. The Subscriber will typically inform the Publisher here, by requesting another item.
• onNext: The onNext method is invoked when another item is made available from the Publisher.
• onError: The onError method is invoked when an error occurs. This usually means that the subscriber will no longer receive any more messages and should be closed down.
• onComplete: The onComplete method is invoked by the publisher...