rxjs#TeardownLogic TypeScript Examples

/**
   * Looks up the context tree for a value associated with the given name.
   *
   * @param  name - The name of the value to return.
   * @param  options - Options to control context lookup.
   * @return An Observable that emits the context value associated with the given key and then completes.
   *         When the requested value is not found in a context, the Observable emits `null` and then completes.
   */
  private lookupContextValue$<T>(name: string, options?: ContextLookupOptions): Observable<T | T[] | null> {
    return new Observable((observer: Observer<T | T[] | null>): TeardownLogic => {
      const replyTo = UUID.randomUUID();
      const unsubscribe$ = new Subject<void>();
      const contextValueLookupRequest = Contexts.newContextValueLookupRequest(name, replyTo, options);

      // Wait until the reply is received.
      Beans.get(MessageClient).observe$<T | T[] | null | undefined>(replyTo)
        .pipe(
          take(1),
          map(reply => reply.headers.get(MessageHeaders.Status) === ResponseStatusCodes.OK ? (reply.body ?? null) : null),
          takeUntil(unsubscribe$),
        )
        .subscribe(observer);

      // Send the request.
      Promise.all([whenSubscribedToReplyTopic(replyTo), this._whenContextTreeChangeListenerInstalled])
        .then(() => window.parent.postMessage(contextValueLookupRequest, '*'))
        .catch(error => observer.error(error));

      return (): void => unsubscribe$.next();
    });
  }

/**
   * Looks up the context names of all values registered in the current and parent contexts.
   *
   * @return An Observable that emits the names of all values registered in the current and parent contexts and then completes.
   */
  private lookupContextNames$(): Observable<Set<string>> {
    return new Observable((observer: Observer<Set<string>>): TeardownLogic => {
      const replyTo = UUID.randomUUID();
      const unsubscribe$ = new Subject<void>();
      const contextNamesLookupRequest = Contexts.newContextTreeNamesLookupRequest(replyTo);

      // Wait until the reply is received.
      Beans.get(MessageClient).observe$<Set<string>>(replyTo)
        .pipe(
          take(1),
          map(reply => reply.headers.get(MessageHeaders.Status) === ResponseStatusCodes.OK ? reply.body! : new Set<string>()),
          takeUntil(unsubscribe$),
        )
        .subscribe(observer);

      // Send the request.
      Promise.all([whenSubscribedToReplyTopic(replyTo), this._whenContextTreeChangeListenerInstalled])
        .then(() => window.parent.postMessage(contextNamesLookupRequest, '*'))
        .catch(error => observer.error(error));
      return (): void => unsubscribe$.next();
    });
  }

public requestReply$<T = any>(channel: MessagingChannel, message: IntentMessage | TopicMessage): Observable<TopicMessage<T>> {
    return new Observable((observer: Observer<TopicMessage>): TeardownLogic => {
      if (isPlatformStopped()) {
        observer.error(GatewayErrors.PLATFORM_STOPPED_ERROR);
        return noop;
      }

      const replyTo = UUID.randomUUID();
      const unsubscribe$ = new Subject<void>();
      const requestError$ = new Subject<never>();

      // Add 'ReplyTo' topic to the message headers where to receive the response(s).
      message.headers.set(MessageHeaders.ReplyTo, replyTo);

      // Receive replies sent to the reply topic.
      merge(this.subscribeToTopic$<T>(replyTo), requestError$)
        .pipe(takeUntil(merge(this._platformStopping$, unsubscribe$)))
        .subscribe({
          next: reply => observer.next(reply),
          error: error => observer.error(error),
          complete: noop, // As per the API, the Observable never completes.
        });

      // Post the request to the broker.
      this.postMessage(channel, message)
        .catch(error => requestError$.error(error));

      return (): void => unsubscribe$.next();
    });
  }

public subscribeToTopic$<T>(topic: string): Observable<TopicMessage<T>> {
    return new Observable((observer: Observer<TopicMessage>): TeardownLogic => {
      if (isPlatformStopped()) {
        observer.error(GatewayErrors.PLATFORM_STOPPED_ERROR);
        return noop;
      }

      const subscriberId = UUID.randomUUID();
      const unsubscribe$ = new Subject<void>();
      const subscribeError$ = new Subject<never>();

      // Receive messages sent to the given topic.
      merge(this.message$, subscribeError$)
        .pipe(
          filterByChannel<TopicMessage>(MessagingChannel.Topic),
          filterByMessageHeader({key: MessageHeaders.ɵTopicSubscriberId, value: subscriberId}),
          pluckMessage(),
          takeUntil(merge(this._platformStopping$, unsubscribe$)),
          finalize(() => this.unsubscribeFromTopic(topic, subscriberId)),
        )
        .subscribe({
          next: reply => observer.next(reply),
          error: error => observer.error(error),
          complete: noop, // As per the API, the Observable never completes.
        });

      // Post the topic subscription to the broker.
      const topicSubscribeMessage: TopicSubscribeCommand = {subscriberId, topic, headers: new Map()};
      this.postMessage(MessagingChannel.TopicSubscribe, topicSubscribeMessage)
        .catch(error => subscribeError$.error(error));

      return (): void => unsubscribe$.next();
    });
  }