过滤状态在哪里？

/**
 * 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);
};

那些选择器是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.