這篇文章帶大家深入了解一下angular的狀態(tài)管理器NgRx，介紹一下NgRx的使用方法，希望對大家有幫助！

NgRx 是 Angular 應(yīng)用程式中實(shí)作全域狀態(tài)管理的 Redux 架構(gòu)解決方案。 【相關(guān)教學(xué)推薦：《angular教學(xué)》】

• #@ngrx/store：全域狀態(tài)管理模組

• @ngrx/effects：處理副作用

• #@ngrx/store-devtools：瀏覽器偵錯(cuò)工具，需要依賴Redux Devtools Extension

• #@ngrx/schematics：命令列工具，快速產(chǎn)生NgRx 檔案

• @ngrx/entity：提高開發(fā)者在Reducer 中操作資料的效率

• @ngrx/router-store：將路由狀態(tài)同步到全域Store

#快速開始

1、下載NgRx

npm install @ngrx/store @ngrx/effects @ngrx/entity @ngrx/router-store @ngrx/store-devtools @ngrx/schematics

2、設(shè)定NgRx CLI

ng config cli.defaultCollection @ngrx/schematics

// angular.json
"cli": {
  "defaultCollection": "@ngrx/schematics"
}

3、建立Store

ng g store State --root --module app.module.ts --statePath store --stateInterface AppState

##4 、建立Action

ng g action store/actions/counter --skipTests

import { createAction } from "@ngrx/store"

export const increment = createAction("increment")
export const decrement = createAction("decrement")

#5、建立Reducer

#ng g reducer store/reducers/counter --skipTests --reducers=../index.ts

import { createReducer, on } from "@ngrx/store"
import { decrement, increment } from "../actions/counter.actions"

export const counterFeatureKey = "counter"

export interface State {
  count: number
}

export const initialState: State = {
  count: 0
}

export const reducer = createReducer(
  initialState,
  on(increment, state => ({ count: state.count + 1 })),
  on(decrement, state => ({ count: state.count - 1 }))
)

6、建立Selector

#ng g selector store/selectors/counter --skipTests

import { createFeatureSelector, createSelector } from "@ngrx/store"
import { counterFeatureKey, State } from "../reducers/counter.reducer"
import { AppState } from ".."

export const selectCounter = createFeatureSelector<AppState, State>(counterFeatureKey)
export const selectCount = createSelector(selectCounter, state => state.count)

7、元件類別觸發(fā)Action、取得狀態(tài)

import { select, Store } from "@ngrx/store"
import { Observable } from "rxjs"
import { AppState } from "./store"
import { decrement, increment } from "./store/actions/counter.actions"
import { selectCount } from "./store/selectors/counter.selectors"

export class AppComponent {
  count: Observable<number>
  constructor(private store: Store<AppState>) {
    this.count = this.store.pipe(select(selectCount))
  }
  increment() {
    this.store.dispatch(increment())
  }
  decrement() {
    this.store.dispatch(decrement())
  }
}

8、元件模板顯示狀態(tài)

<button (click)="increment()">+</button>
<span>{{ count | async }}</span>
<button (click)="decrement()">-</button>

Action Payload

1、在元件中使用dispatch 觸發(fā)Action 時(shí)傳遞參數(shù)，參數(shù)最終會被放置在Action 物件中。

this.store.dispatch(increment({ count: 5 }))

2、建立 Action Creator 函數(shù)時(shí)，取得參數(shù)並指定參數(shù)類型。

import { createAction, props } from "@ngrx/store"
export const increment = createAction("increment", props<{ count: number }>())

export declare function props<P extends object>(): Props<P>;

3、在 Reducer 中透過 Action 物件取得參數(shù)。

export const reducer = createReducer(
  initialState,
  on(increment, (state, action) => ({ count: state.count + action.count }))
)

MetaReducer

metaReducer 是 Action -> Reducer 之間的鉤子，允許開發(fā)者對 Action 進(jìn)行預(yù)處理 (在普通 Reducer 函數(shù)呼叫之前呼叫)。

function debug(reducer: ActionReducer<any>): ActionReducer<any> {
  return function (state, action) {
    return reducer(state, action)
  }
}

export const metaReducers: MetaReducer<AppState>[] = !environment.production
  ? [debug]
  : []

Effect

需求：在頁面中新增一個(gè)按鈕，點(diǎn)擊按鈕後延遲一秒鐘讓數(shù)值增加。

1、在元件模板中新增一個(gè)用於非同步數(shù)值增加的按鈕，按鈕被點(diǎn)擊後執(zhí)行

increment_async 方法

<button (click)="increment_async()">async</button>

2、在元件類別中新增

increment_async 方法，並在方法中觸發(fā)執(zhí)行非同步操作的Action

increment_async() {
  this.store.dispatch(increment_async())
}

3、在Action 檔案中新增執(zhí)行非同步操作的Action

export const increment_async = createAction("increment_async")

4、創(chuàng)建Effect，接收Action 並執(zhí)行副作用，繼續(xù)觸發(fā)Action

ng g effect store/effects/counter --root --module app.module.ts --skipTests

Effect 功能由@ngrx/effects 模組提供，所以在根模組中需要導(dǎo)入相關(guān)的模組依賴

import { Injectable } from "@angular/core"
import { Actions, createEffect, ofType } from "@ngrx/effects"
import { increment, increment_async } from "../actions/counter.actions"
import { mergeMap, map } from "rxjs/operators"
import { timer } from "rxjs"

// createEffect
// 用于創(chuàng)建 Effect, Effect 用于執(zhí)行副作用.
// 調(diào)用方法時(shí)傳遞回調(diào)函數(shù), 回調(diào)函數(shù)中返回 Observable 對象, 對象中要發(fā)出副作用執(zhí)行完成后要觸發(fā)的 Action 對象
// 回調(diào)函數(shù)的返回值在 createEffect 方法內(nèi)部被繼續(xù)返回, 最終返回值被存儲在了 Effect 類的屬性中
// NgRx 在實(shí)例化 Effect 類后, 會訂閱 Effect 類屬性, 當(dāng)副作用執(zhí)行完成后它會獲取到要觸發(fā)的 Action 對象并觸發(fā)這個(gè) Action

// Actions
// 當(dāng)組件觸發(fā) Action 時(shí), Effect 需要通過 Actions 服務(wù)接收 Action, 所以在 Effect 類中通過 constructor 構(gòu)造函數(shù)參數(shù)的方式將 Actions 服務(wù)類的實(shí)例對象注入到 Effect 類中
// Actions 服務(wù)類的實(shí)例對象為 Observable 對象, 當(dāng)有 Action 被觸發(fā)時(shí), Action 對象本身會作為數(shù)據(jù)流被發(fā)出

// ofType
// 對目標(biāo) Action 對象進(jìn)行過濾.
// 參數(shù)為目標(biāo) Action 的 Action Creator 函數(shù)
// 如果未過濾出目標(biāo) Action 對象, 本次不會繼續(xù)發(fā)送數(shù)據(jù)流
// 如果過濾出目標(biāo) Action 對象, 會將 Action 對象作為數(shù)據(jù)流繼續(xù)發(fā)出

@Injectable()
export class CounterEffects {
  constructor(private actions: Actions) {
    // this.loadCount.subscribe(console.log)
  }
  loadCount = createEffect(() => {
    return this.actions.pipe(
      ofType(increment_async),
      mergeMap(() => timer(1000).pipe(map(() => increment({ count: 10 }))))
    )
  })
}

Entity

##1、概述Entity 譯為實(shí)體，實(shí)體就是集合中的一條資料。

NgRx 中提供了實(shí)體適配器對象，在實(shí)體適配器物件下面提供了各種操作集合中實(shí)體的方法，目的就是提高開發(fā)者操作實(shí)體的效率。

2、核心##1、EntityState：實(shí)體類型介面

/*
	{
		ids: [1, 2],
		entities: {
			1: { id: 1, title: "Hello Angular" },
			2: { id: 2, title: "Hello NgRx" }
		}
	}
*/
export interface State extends EntityState<Todo> {}

2、createEntityAdapter： 建立實(shí)體適配器物件

3、EntityAdapter：實(shí)體適配器物件類型介面

export const adapter: EntityAdapter<Todo> = createEntityAdapter<Todo>()
// 獲取初始狀態(tài) 可以傳遞對象參數(shù) 也可以不傳
// {ids: [], entities: {}}
export const initialState: State = adapter.getInitialState()

#3、實(shí)例方法

##https://ngrx.io /guide/entity/adapter#adapter-collection-methods

#4、選擇器

##

// selectTotal 獲取數(shù)據(jù)條數(shù)
// selectAll 獲取所有數(shù)據(jù) 以數(shù)組形式呈現(xiàn)
// selectEntities 獲取實(shí)體集合 以字典形式呈現(xiàn)
// selectIds 獲取id集合, 以數(shù)組形式呈現(xiàn)
const { selectIds, selectEntities, selectAll, selectTotal } = adapter.getSelectors();

export const selectTodo = createFeatureSelector<AppState, State>(todoFeatureKey)
export const selectTodos = createSelector(selectTodo, selectAll)

#Router Store

1、同步路由狀態(tài)

1）引入模組

import { StoreRouterConnectingModule } from "@ngrx/router-store"

@NgModule({
  imports: [
    StoreRouterConnectingModule.forRoot()
  ]
})
export class AppModule {}

2）將路由狀態(tài)整合到Store

import * as fromRouter from "@ngrx/router-store"

export interface AppState {
  router: fromRouter.RouterReducerState
}
export const reducers: ActionReducerMap<AppState> = {
  router: fromRouter.routerReducer
}

2、建立取得路由狀態(tài)的Selector

// router.selectors.ts
import { createFeatureSelector } from "@ngrx/store"
import { AppState } from ".."
import { RouterReducerState, getSelectors } from "@ngrx/router-store"

const selectRouter = createFeatureSelector<AppState, RouterReducerState>(
  "router"
)

export const {
  // 獲取和當(dāng)前路由相關(guān)的信息 (路由參數(shù)、路由配置等)
  selectCurrentRoute,
  // 獲取地址欄中 # 號后面的內(nèi)容
  selectFragment,
  // 獲取路由查詢參數(shù)
  selectQueryParams,
  // 獲取具體的某一個(gè)查詢參數(shù) selectQueryParam(&#39;name&#39;)
  selectQueryParam,
  // 獲取動態(tài)路由參數(shù)
  selectRouteParams,
 	// 獲取某一個(gè)具體的動態(tài)路由參數(shù) selectRouteParam(&#39;name&#39;)
  selectRouteParam,
  // 獲取路由自定義數(shù)據(jù)
  selectRouteData,
  // 獲取路由的實(shí)際訪問地址
  selectUrl
} = getSelectors(selectRouter)

// home.component.ts
import { select, Store } from "@ngrx/store"
import { AppState } from "src/app/store"
import { selectQueryParams } from "src/app/store/selectors/router.selectors"

export class AboutComponent {
  constructor(private store: Store<AppState>) {
    this.store.pipe(select(selectQueryParams)).subscribe(console.log)
  }
}

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