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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

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:

NameTypeAttributeDescription
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:

NameTypeAttributeDescription
value T

The next value.

Return:

void