RxJava - How Observable works

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Observables represents the sources of data where as Observers (Subscribers) listen to them. In nutshell, an Observable emits items and a Subscriber then consumes these items.

Observable

• Observable provides data once subscriber starts listening.

• Observable can emit any number of items.

• Observable can emit only signal of completion as well with no item.

• Observable can terminate successfully.

• Observable may never terminate. e.g. a button can be clicked any number of times.

• Observable may throw error at any point of time.

Subscriber

• Observable can have multiple subscribers.

• When an Observable emits an item, each subscriber onNext() method gets invoked.

• When an Observable finished emitting items, each subscriber onComplete() method gets invoked.

• If an Observable emits error, each subscriber onError() method gets invoked.