angular - 为 ngrx/data 实体创建选择器

Question

我有一个状态，我想从 ngrx/data 实体创建选择器。

import {
  Action,
  ActionReducer,
  ActionReducerMap,
  createFeatureSelector,
  createSelector,
  MetaReducer
} from '@ngrx/store';
import {environment} from '../../environments/environment';
import * as fromRouter from '@ngrx/router-store';
import * as fromDrawer from './drawer';
import {InjectionToken} from '@angular/core';
import {NavigationItem} from '../models/navigation-item';

export interface State {
  router: fromRouter.RouterReducerState<any>;
  drawerNavigationItems: fromDrawer.State;
}

export const ROOT_REDUCERS = new InjectionToken<ActionReducerMap<State, Action>>('Root reducers token', {factory: () => ({
    router: fromRouter.routerReducer,
    drawerNavigationItems: fromDrawer.reducer,
  }),
});

export const metaReducers: MetaReducer<State>[] = !environment.production ? [] : [];

export const selectRouter = createFeatureSelector<
  State,
  fromRouter.RouterReducerState<any>
  >('router');

const {
  selectQueryParams,    // select the current route query params
  selectQueryParam,     // factory function to select a query param
  selectRouteParams,    // select the current route params
  selectRouteParam,     // factory function to select a route param
  selectRouteData,      // select the current route data
  selectUrl,            // select the current url
} = fromRouter.getSelectors(selectRouter);

export const selectRouteId = selectRouteParam('id');
export const selectStatus = selectQueryParam('status');


// Drawer

export const selectDrawerNavigationItems = (state: State) => state.drawerNavigationItems.items as NavigationItem[];

如何使用预定义的选择器或使用来自 ngrx/data 的实体或服务编写自己的选择器？

作为示例，我想创建一个选择器来选择所有“社区”实体，然后在第 2 步中通过 selectRouteId 选择 1。如果您想象一条路线 /communities/:id，selectRouteId 返回 Id，现在我想要来自 CommunityService 的数据并使用在步骤 1 中创建或以某种方式导入和使用的选择器，并返回结果 1 Community 和 selectRouteId 的 id，因此我稍后可以执行类似 this 的操作.store.dispatch(selectCommunityByCurrentRouteId);

此问题特定于@ngrx/data。

Answer 1

补充答案，具体回答我自己的问题，这是reducers/index.ts 现在的样子

import {
  Action,
  ActionReducer,
  ActionReducerMap,
  createFeatureSelector,
  createSelector,
  MetaReducer
} from '@ngrx/store';
import {environment} from '../../environments/environment';
import * as fromRouter from '@ngrx/router-store';
import * as fromDrawer from './drawer';
import {InjectionToken} from '@angular/core';
import {NavigationItem} from '../models/navigation-item';
import {EntitySelectorsFactory} from '@ngrx/data';
import {Community} from '../models/community';

export interface State {
  router: fromRouter.RouterReducerState<any>;
  drawerNavigationItems: fromDrawer.State;
}

export const ROOT_REDUCERS = new InjectionToken<ActionReducerMap<State, Action>>('Root reducers token', {factory: () => ({
    router: fromRouter.routerReducer,
    drawerNavigationItems: fromDrawer.reducer,
  }),
});

export const metaReducers: MetaReducer<State>[] = !environment.production ? [] : [];

export const selectRouter = createFeatureSelector<
  State,
  fromRouter.RouterReducerState<any>
  >('router');

const {
  selectQueryParams,    // select the current route query params
  selectQueryParam,     // factory function to select a query param
  selectRouteParams,    // select the current route params
  selectRouteParam,     // factory function to select a route param
  selectRouteData,      // select the current route data
  selectUrl,            // select the current url
} = fromRouter.getSelectors(selectRouter);

export const selectRouteId = selectRouteParam('id');
// export const selectStatus = selectQueryParam('status');

// Data

export const communitySelectors = new EntitySelectorsFactory().create<Community>('Community');

export const selectCommunityByRouteId = createSelector(
  selectRouteId,
  communitySelectors.selectEntities,
  (id, communities) => communities.find(c => c.id === id)
);


// Drawer

export const selectDrawerNavigationItems = (state: State) => state.drawerNavigationItems.items as NavigationItem[];

您可以使用以下命令为社区模型创建选择器

export const communitySelectors = new EntitySelectorsFactory().create<Community>('Community');

然后将这两者结合起来并通过路由 ID 返回 1 Community。

export const selectCommunityByRouteId = createSelector(
  selectRouteId,
  communitySelectors.selectEntities,
  (id, communities) => communities.find(c => c.id === id)
);

非常简单，您选择输入流，提供投影函数并返回结果。

稍后，在组件中

export class OneCommunityComponent implements OnInit {
  community$: Observable<Community>;
  constructor(
    private store: Store<State>,
  ) {
  this.community$ = this.store.select(selectCommunityByRouteId);
  }
}