public interface | source

Observer

An interface for a consumer of push-based notifications delivered by an Observable.

interface Observer<T> {
  closed?: boolean;
  next: (value: T) => void;
  error: (err: any) => void;
  complete: () => void;
}

An object conforming to the Observer interface is usually given to the observable.subscribe(observer) method, and the Observable will call the Observer's next(value) method to provide notifications. A well-behaved Observable will call an Observer's complete() method exactly once or the Observer's error(err) method exactly once, as the last notification delivered.

Member Summary

Public Members
public	closed: boolean An optional flag to indicate whether this Observer, when used as a subscriber, has already been unsubscribed from its Observable.

Method Summary

Public Methods
public	complete(): void The callback to receive a valueless notification of type `complete` from the Observable.
public	error(err: any): void The callback to receive notifications of type `error` from the Observable, with an attached Error.
public	next(value: T): void The callback to receive notifications of type `next` from the Observable, with a value.

Public Members

public closed: boolean source

An optional flag to indicate whether this Observer, when used as a subscriber, has already been unsubscribed from its Observable.

Public Methods

public complete(): void source

The callback to receive a valueless notification of type complete from the Observable. Notifies the Observer that the Observable has finished sending push-based notifications.

Return:

void

public error(err: any): void source

The callback to receive notifications of type error from the Observable, with an attached Error. Notifies the Observer that the Observable has experienced an error condition.

Params:

Name	Type	Attribute	Description
err	any		The `error` exception.

Return:

void

public next(value: T): void source

The callback to receive notifications of type next from the Observable, with a value. The Observable may call this method 0 or more times.

Params:

Name	Type	Attribute	Description
value	T		The `next` value.

Return:

void