#Angular状态管理-Ngrx

#官网介绍

• Managing global and local state.
• Isolation of side effects to promote a cleaner component architecture.
• Entity collection management.
• Integration with the Angular Router.
• Developer tooling that enhances developer experience when building many different types of applications.

#流程图

#基本概念

#actions

代表一个应用中唯一发生的事件

interface Action {
	type: string;  // [Source] description
}
// 举个栗子
{
	type: '[Auth API] Login Success'
}
{
  type: '[Login Page] Login',
  username: string;
  password: string;
}

actions 用法

定义

import { createAction, props } from '@ngrx/store';

export const login = createAction(
  '[Login Page] Login',
  props<{ username: string; password: string }>()
);

调用

onSubmit(username: string, password: string) {
  store.dispatch(login({ username: username, password: password }));
}

#reducers

根据 action 的类型通过一个纯函数来更新 state

用法

const scoreboardReducer = createReducer(
  initialState,
  on(ScoreboardPageActions.homeScore, state => ({ ...state, home: state.home + 1 })),
  on(ScoreboardPageActions.awayScore, state => ({ ...state, away: state.away + 1 })),
  on(ScoreboardPageActions.resetScore, state => ({ home: 0, away: 0 })),
  on(ScoreboardPageActions.setScores, (state, { game }) => ({ home: game.home, away: game.away }))
);

export function reducer(state: State | undefined, action: Action) {
  return scoreboardReducer(state, action);
}

#selectors

selectors 是用来获取当前状态的一个纯函数 ngrx 提供了 createSelector 和 createFeatureSelector 来创建 selector

#工作流

1. 定义 state
2. 编写 aciton，定义一个数据可以有哪些操作
3. 编写 reducer，使用 createReducer 方法，定义哪些 action 的触发需要对 state 做哪些修改，on 的第二个参数必须为纯函数
4. 在 module 文件里的 StoreModule.forRoot 方法传入新定义的 state 与之对应的 reducer
5. 利用 selector 来获取当前 state
6. 利用 dispatch 方法触发 action