unsubscribe-02.ts

export class AppComponent implements OnInit, OnDestroy {
  @Selector(CustomersState.SelectedCustomer)
  private selectedCustomer$: Observable<Customer>;

  @Selector(OrdersState.NewOrder)
  private newOrder$: Observable<Order>;

  private onComponentDestroy$: Subject<void>;

  constructor() {
    this.onComponentDestroy$ = new Subject();
  }

  ngOnInit() {
    this.selectedCustomer$
      .pipe(takeUntil(this.onComponentDestroy$))
      .subscribe(customer => {
        // Do something
      });

    this.newOrder$
      .pipe(takeUntil(this.onComponentDestroy$))
      .subscribe(order => {
        // Do something
      });
  }

  ngOnDestroy() {
    this.onComponentDestroy$.next();
  }
}