gistfile1.txt

@Injectable()
export class CategoriesGuard implements CanActivate {
  constructor(private store: Store<fromStore.CategoriesState>) {}

  canActivate(): Observable<boolean> {
    return this.checkStore().pipe(
      switchMap(() => of(true)),
      catchError(() => of(false))
    );
  }

  checkStore(): Observable<boolean> {
    return this.store.select(fromStore.selectCategoriesLoaded).pipe(
      tap(loaded => {
        if (!loaded) {
          this.store.dispatch(new fromStore.LoadCategories());
        }
      }),
      take(1)
    );
  }
}