小编Хри*_*тов的帖子

我有产品服务，我想从州获得最好的产品。

我可以实现此目的的一种方法是使用rxjs如下所示：

 @Injectable({ providedIn: 'root' })
 export class ProductDataService extends EntityCollectionServiceBase<Product> {
  
    bestProductsIds$ = new BehaviorSubject([]);

    bestProducts$ = combineLatest([this.entities$, this.bestProductsIds$]).pipe(
      map(([products, ids]) => products.filter((p) => ids.includes(p.id))),
      map((products) => orderBy(product, ['createdDate', ['desc']])),
      map((products) => this.toProductCard(products))
    );
}

另一种方法是使用选择器：

export const selectBestProducts = createSelector(
  ([products, ids]) => products.filter((p) => ids.includes(p.id)),
  (products) => orderBy(products, ['createdDate', ['desc']])
);


@Injectable({ providedIn: 'root' })
export class ProductDataService extends EntityCollectionServiceBase<Product> {

  bestProductsIds$ = new BehaviorSubject([]);

  bestProducts$ = combineLatest([this.entities$, this.bestProductsIds$]).pipe(select(selectBestProducts));

  ...
}

我知道 ngrx 选择器是记忆函数，但我在这里使用combineLatest …