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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
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Observable provides data once subscriber starts listening.
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Observable can emit any number of items.
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Observable can emit only signal of completion as well with no item.
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Observable can terminate successfully.
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Observable may never terminate. e.g. a button can be clicked any number of times.
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Observable may throw error at any point of time.
Subscriber
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Observable can have multiple subscribers.
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When an Observable emits an item, each subscriber onNext() method gets invoked.
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When an Observable finished emitting items, each subscriber onComplete() method gets invoked.
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If an Observable emits error, each subscriber onError() method gets invoked.
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