过滤状态在哪里？

Question

新手问题：我有一个使用ngrx的angular2应用程序，我有一个服务，它将状态（可观察数组）返回给一个组件。

我的问题是，如果我想在组件中使用它的只读子集，我在哪里过滤状态？

我是否在减速机，服务或组件中执行此操作？

Answer 1

可以在ngrx example application中找到一些指导。有一种模式，其中定义了选择器alongside reducers：

/**
 * 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);
};

这些选择器是used in (smart) components来选择/过滤状态：

...
export class CollectionPage {

  books$: Observable<BooksInput>;

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

此模式/机制可用于过滤组件或服务中的状态 - 最适合您的体系结构。