Method subscribe

packages/y-graph-storage/src/YGraph.ts:57–76

* Subscribe to changes to the graph. * @param observer The observer to subscribe to. * @returns A function to unsubscribe from the changes.

(observer: Observer<YGraphChange>)

   * @returns A function to unsubscribe from the changes.
   */
  public subscribe(observer: Observer<YGraphChange>) {
    const subscribers = this.#subscribers;
    subscribers.add(observer);
    if (this.#subscription === undefined) {
      this.#subscription = createGraphObserver(this).subscribe({
        next(value) {
          for (const subscriber of subscribers) {
            subscriber.next?.(value);
          }
        },
      });
    }
    return () => {
      subscribers.delete(observer);
      if (subscribers.size === 0) {
        this.#subscription?.unsubscribe();
        this.#subscription = undefined;
      }
    };
  }

  /**
   * Create a live query.