本文将会示范如何使用NgRx/Store 4和Angular5。@ngrx/store是基于RxJS的状态管理库，其灵感来源于Redux。在NgRx中，状态是由一个包含action和reducer的函数的映射组成的。Reducer函数经由action的分发以及当前或初始的状态而被调用，最后由reducer返回一个不可变的状态。你可以在@ngrx/store中找到我们将在下面的例子中讨论到的相关的API。
Action: Action是状态的改变。它描述了某个事件的发生，但是没有指定应用的状态如何改变。
ActionReducerMap： ActionReducerMap注册了一系列的reducer，在应用中使用StoreModule对它进行配置。
ActionReducer: 它被用于创建reducer，例如logger。
MetaReducer: 在应用中使用StoreModule配置的MetaReducer构成了根的meta-reducer。
StoreModule: StoreModule是@ngrx/storeAPI中的一个模块，它被用来在应用模块中配置reducer。
createFeatureSelector: 它为状态（state）创建一个feature selector。
createSelector: 它创建一个selector用于生成一个指定的状态。
Store: 它提供了Store.select()和Store.dispatch()来与reducer协同工作。Store.select()用于选择一个selector，Store.dispatch()用于向reducer分发action的类型。
1. 使用到的技术
下面是我们的例子中用到的技术：
Angular 5.0.0
Angular CLI 1.5.0
NgRx/Store 4.1.1
TypeScript 2.4.2
Node.js 6.11.0
NPM 3.10.10
2. 安装Angular CLI和NgRX/Store
确保已安装的Node和NPM的最低版本为：Node 6.9.x和NPM 3.x.x
在命令行中输入以下命令：
npm install -g @angular/cli
运行以下命令生成一个新的项目：
ng new my-app
现在安装
@ngrx/store。使用命令行进入my-app目录，然后运行如下命令：
npm i @ngrx/store --save
现在我们已经准备好使用NgRx/Store和Angular了。
3. 创建State
State是一个单独的不可变的数据结构。我们会像如下这样创建state：
export interface AppState {
articleState: ArticleState;
}
export interface ArticleState {
articles: Article[];
}
4. 创建Action类
NgRx的Action描述了状态的变化。对于每一个action，我们都需要创建一个继承自Action的类，同时定义其type和payload（payload是个可选参数）。
export const JAVA = 'Java';
export const MY_ARTICLES = 'Favorite_Articles';
export class JavaArticlesAction implements Action {
readonly type = JAVA;
}
export class FavoriteArticlesAction implements Action {
readonly type = MY_ARTICLES;
constructor(public payload: Article[]) {}
}
5. 创建Reducer
Reducer描述了任何一个action所对应的应用的state将怎样变化。reducer创建如下：
export function reducer(state = initialState, action: fromActions.All): ArticleState {
switch(action.type) {
case fromActions.JAVA: {
return {articles: JAVA_ARTICLES};
}
case fromActions.ANGULAR: {
return {articles: ANGULAR_ARTICLES};
}
case fromActions.MY_ARTICLES: {
return {articles: action.payload};
}
default: {
return state;
}
}
}
6. 使用createFeatureSelector和createSelector()
createFeatureSelector()被用于为任意指定的state创建一个feature selector。
export const getArticleState = createFeatureSelector<ArticleState>('articleState');
createSelector()使用feature selector来创建selector。
export const getArticles = createSelector(
getArticleState,
(state: ArticleState) => state.articles
);
7. 使用ActionReducerMap
ActionReducerMap注册了reducer。我们需要在我们配置我们的reducer的地方创建一个 ActionReducerMap的常量。然后在应用模块中使用StoreModule来配置这个常量。
export const reducers: ActionReducerMap<AppState> = {
articleState: articleReducer.reducer
};
8.使用ActionReducer
ActionReducer用来创建类似logger的reducer，使用MetaReducer对它进行配置。
export function logger(reducer: ActionReducer<AppState>): ActionReducer<AppState> {
return function(state: AppState, action: any): AppState {
console.log('state', state);
console.log('action', action);
return reducer(state, action);
};
}
通过使用上面的代码，我们可以在控制台中获取每个action的状态和名称。
9.使用MetaReducer
MetaReducer由我们所创建的一系列ActionReducer所组成。在应用中使用StoreModule配置的MetaReducer构成了根meta-reducer。@ngrx/store默认使用 combineReducers在创建根meta-reducer。
export const metaReducers: MetaReducer<AppState>[] = !environment.production
? [logger]
: [];
10. 使用StoreModule
StoreModule是@ngrx/storeAPI中的一个模块，它被用来在应用模块中配置reducer。
@NgModule({
imports: [
---
StoreModule.forRoot(reducers, {metaReducers})
]
---
})
11. 使用Store.select()和Store.dispatch()
Store.select()和 Store.dispatch()与是reducer配合使用的。Store.select()用于选择一个selector，Store.dispatch()用于向reducer分发action的类型。
要使用Store, 在组件中创建一个Observable类型的属性。
articles: Observable<Article[]>
现在使用依赖注入来实例化Store，然后选择一个selector。
constructor(private store: Store<ArticleState>) {
this.articles = store.select(articleReducer.getArticles);
}
现在分发这个action以通过reducer改变state。
showJavaArticles(){
this.store.dispatch(new fromActions.JavaArticlesAction());
}
12. 完整的例子
下面是我们的例子的项目结构：
my-app
|
|--src
| |
| |--app
| | |
| | |--actions
| | | |
| | | |--article.actions.ts
| | |
| | |--components
| | | |
| | | |--article.component.html
| | | |--article.component.ts
| | |
| | |--models
| | | |
| | | |--article.ts
| | |
| | |--reducers
| | | |
| | | |--app.states.ts
| | | |--article.reducer.ts
| | | |--reducers.ts
| | |
| | |--app.component.ts
| | |--app.module.ts
| |
| |--main.ts
| |--index.html
| |--styles.css
|
|--node_modules
|--package.json
以下是完整的代码：
article.actions.ts
import { Action } from '@ngrx/store';
import { Article } from '../models/article';
export const JAVA = 'Java';
export const ANGULAR = 'Angular';
export const MY_ARTICLES = 'Favorite_Articles';
export class JavaArticlesAction implements Action {
readonly type = JAVA;
}
export class AngularArticlesAction implements Action {
readonly type = ANGULAR;
}
export class FavoriteArticlesAction implements Action {
readonly type = MY_ARTICLES;
constructor(public payload: Article[]) {}
}
export type All = JavaArticlesAction | AngularArticlesAction | FavoriteArticlesAction;
article.ts
export interface Article {
id: number;
title: string;
category: string;
}
export const JAVA_ARTICLES: Article[] = [
{id: 1, title: 'Java Article 1', category: 'Java'},
{id: 2, title: 'Java Article 2', category: 'Java'},
]
export const ANGULAR_ARTICLES: Article[] = [
{id: 1, title: 'Angular Article 1', category: 'Angular'},
{id: 2, title: 'Angular Article 2', category: 'Angular'},
]
export const FAVORITE_ARTICLES: Article[] = [
{id: 1, title: 'Java Article 1', category: 'Java'},
{id: 2, title: 'Angular Article 2', category: 'Angular'}
]
app.states.ts
import { Article } from '../models/article';
export interface AppState {
articleState: ArticleState;
}
export interface ArticleState {
articles: Article[];
}
article.reducer.ts
import { createFeatureSelector, createSelector } from '@ngrx/store';
import * as fromActions from '../actions/article.actions';
import { JAVA_ARTICLES, ANGULAR_ARTICLES } from '../models/article';
import { ArticleState } from './app.states';
export const initialState: ArticleState = { articles: []};
export function reducer(state = initialState, action: fromActions.All): ArticleState {
switch(action.type) {
case fromActions.JAVA: {
return {articles: JAVA_ARTICLES};
}
case fromActions.ANGULAR: {
return {articles: ANGULAR_ARTICLES};
}
case fromActions.MY_ARTICLES: {
return {articles: action.payload};
}
default: {
return state;
}
}
}
export const getArticleState = createFeatureSelector<ArticleState>('articleState');
export const getArticles = createSelector(
getArticleState,
(state: ArticleState) => state.articles
);
reducer.ts
import { ActionReducerMap, ActionReducer, MetaReducer } from '@ngrx/store';
import { AppState } from './app.states';
import * as articleReducer from './article.reducer';
import { environment } from '../../environments/environment';
export const reducers: ActionReducerMap<AppState> = {
articleState: articleReducer.reducer
};
export function logger(reducer: ActionReducer<AppState>): ActionReducer<AppState> {
return function(state: AppState, action: any): AppState {
console.log('state', state);
console.log('action', action);
return reducer(state, action);
};
}
export const metaReducers: MetaReducer<AppState>[] = !environment.production
? [logger]
: [];
article.component.ts
import { Store } from '@ngrx/store';
import { Component } from '@angular/core';
import { Observable } from 'rxjs/Observable';
import * as articleReducer from '../reducers/article.reducer';
import * as fromActions from '../actions/article.actions';
import { ArticleState } from '../reducers/app.states';
import { Article, FAVORITE_ARTICLES } from '../models/article';
@Component({
selector: 'app-article',
templateUrl: 'article.component.html'
})
export class ArticleComponent {
articles: Observable<Article[]>
constructor(private store: Store<ArticleState>) {
this.articles = store.select(articleReducer.getArticles);
}
showJavaArticles(){
this.store.dispatch(new fromActions.JavaArticlesAction());
}
showAngularArticles(){
this.store.dispatch(new fromActions.AngularArticlesAction());
}
showFavoriteArticles(){
this.store.dispatch(new fromActions.FavoriteArticlesAction(FAVORITE_ARTICLES));
}
}
article.component.html
<button (click)="showJavaArticles()">Java Articles</button>
<button (click)="showAngularArticles()">Angular Articles</button>
<button (click)="showFavoriteArticles()">Favorite Articles</button>
<ul>
<li *ngFor="let article of articles | async">
{{article.id}} - {{article.title}} - {{article.category}}
</li>
</ul>
app.component.ts
import { Component } from '@angular/core';
@Component({
selector: 'app-root',
template: `
<app-article></app-article>
`
})
export class AppComponent {
}
app.module.ts
import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { StoreModule } from '@ngrx/store';
import { AppComponent } from './app.component';
import { ArticleComponent } from './components/article.component';
import { reducers, metaReducers } from './reducers/reducers';
@NgModule({
imports: [
BrowserModule,
StoreModule.forRoot(reducers, {metaReducers})
],
declarations: [
AppComponent,
ArticleComponent
],
providers: [
],
bootstrap: [
AppComponent
]
})
export class AppModule { }
原文地址：NgRx/Store 4 + Angular 5 Tutorial
本文由本人原创翻译，转载请注明出处：https://www.jianshu.com/p/c2d61fc76128