subscription-tracker-mixin.ts

type Constructor<T = {}> = new (...args: any[]) => T;

function SubscriptionTrackerMixin<TBase extends Constructor>(Base: TBase) {
  return class extends Base implements OnDestroy {

    private subscriptions: Subscription[]  = [];

    public subscribe<T>(
      observable: Observable<T>,
      observerOrNext?: PartialObserver<T> | ((value: T) => void),
      error?: (error: any) => void,
      complete?: () => void): Subscription {
      const subscription = observable.subscribe(
         toSubscriber(observerOrNext, error, complete)
      );
      this.subscriptions.push(subscription);
      return subscription;
    }

    public unsubscribe(subscription: Subscription) {
      const indexOfSubscription = this.subscriptions.indexOf(subscription);
      if (indexOfSubscription == -1) {
        throw new Error("Unsubscribing to untracked subscription");
      }
      subscription.unsubscribe();
      this.subscriptions.splice(indexOfSubscription, 1);
      return subscription;
    }

    unsubscribeAll() {
      this.subscriptions.forEach((subscription) => subscription.unsubscribe());
      this.subscriptions = [];
    }

    ngOnDestroy() {
      this.unsubscribeAll();
    }
  };
}