在哪里过滤状态？

Question

新手问题：我有一个使用ngrx的angular2应用程序，我有一个服务返回状态（一组可观察对象）给组件。

我的问题是，如果我想在组件中使用只读子集进行过滤，那么我在哪里过滤状态？

我应该在reducer、service还是component中做呢？

- user3253156

Answer 1

可以在ngrx示例应用中找到一些指导。有一个模式是定义选择器与reducer一起定义：

/**
 * Because the data structure is defined within the reducer it is optimal to
 * locate our selector functions at this level. If store is to be thought of
 * as a database, and reducers the tables, selectors can be considered the
 * queries into said database. Remember to keep your selectors small and
 * focused so they can be combined and composed to fit each particular
 * use-case.
 */
export function getBookEntities() {
  return (state$: Observable<BooksState>) => state$
    .select(s => s.entities);
};

这些选择器被用于（智能）组件中来选择/过滤状态：

在这里查看代码示例

...
export class CollectionPage {

  books$: Observable<BooksInput>;

  constructor(store: Store<AppState>) {
    this.books$ = store.let(getBookCollection());
  }
}

这种模式/机制可以用于过滤组件或服务中的状态 - 无论哪种最适合您的架构。

- cartant