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MobX 用于状态管理,简单高效。本文将于 React 上介绍如何开始,包括了:

  • 了解 MobX 概念
  • 从零准备 React 应用
  • MobX React.FC 写法
  • MobX React.Component 写法

可以在线体验: https://ikuokuo.github.io/start-react ,代码见: https://github.com/ikuokuo/start-react

概念

首先,ui 是由 state 通过 fn 生成:

ui = fn(state)

在 React 里, fn 即组件,依照自己的 state 渲染。

如果 state 是共享的,一处状态更新,多处组件响应呢?这时就可以用 MobX 了。

MobX 数据流向如下:

      ui
    ↙    ↖
action → state

ui 触发 action,更新 state,重绘 ui。注意是单向的。

了解更多,请阅读 MobX 主旨 。这里讲下实现时的主要步骤:

  • 定义数据存储类 Data Store
    • 成员属性为 state,成员函数为 action
    • mobx 标记为 observable
  • 定义 Stores Provider
    • 方式一 React.ContextcreateContext 包装 Store 实例,ui useContext 使用
    • 方式二 mobx-react.Provider:直接包装 Store 实例,提供给 Providerui inject 使用
  • 实现 ui 组件
    • mobx 标记为 observer
    • 获取 stores,直接引用 state
    • 若要更新 state,间接调用 action

项目结构上就是多个 stores 目录,定义各类 storestate action,异步操作也很简单。了解更多,请阅读:

准备

React App

yarn create react-app start-react --template typescript
cd start-react

React Router

路由库,以便导航样例。

yarn add react-router-dom

Antd

组件库,以便布局 UI。

yarn add antd @ant-design/icons

高级配置

yarn add @craco/craco -D
yarn add craco-less

craco.config.js 配置了深色主题:

const path = require('path');
const CracoLessPlugin = require('craco-less');
const { getThemeVariables } = require('antd/dist/theme');

module.exports = {
  plugins: [
    {
      plugin: CracoLessPlugin,
      options: {
        lessLoaderOptions: {
          lessOptions: {
            modifyVars: getThemeVariables({
              dark: true,
              // compact: true,
            }),
            javascriptEnabled: true,
          },
        },
      },
    },
  ],
  webpack: {
    alias: { '@': path.resolve(__dirname, './src') },
  },
};

ESLint

VSCode 安装 ESLint Prettier 扩展。初始化 eslint

$ npx eslint --init
✔ How would you like to use ESLint? · style
✔ What type of modules does your project use? · esm
✔ Which framework does your project use? · react
✔ Does your project use TypeScript? · No / Yes
✔ Where does your code run? · browser
✔ How would you like to define a style for your project? · guide
✔ Which style guide do you want to follow? · airbnb
✔ What format do you want your config file to be in? · JavaScript

配置 .eslintrc.js .eslintignore .vscode/settings.json,详见代码。并于 package.json 添加:

"scripts": {
  "lint": "eslint . --ext .js,.jsx,.ts,.tsx --ignore-pattern node_modules/"
},

执行 yarn lint 通过, yarn start 运行。

到此, React Antd 应用就准备好了。初始模板如下,可见首个提交:

MobX

yarn add mobx mobx-react

mobx-react 包含了 mobx-react-lite,所以不必安装了。

  • 如果只用 React.FC (HOOK) 时,用 mobx-react-lite 即可。
  • 如果要用 React.Component (Class) 时,用 mobx-react 才行。

mobx-react-lite 与 React.FC

定义 Data Stores

makeAutoObservable

定义数据存储模型后,于构造函数里调用 makeAutoObservable(this) 即可。

stores/Counter.ts:

import { makeAutoObservable } from 'mobx';

class Counter {
  count = 0;

  constructor() {
    makeAutoObservable(this);
  }

  increase() {
    this.count += 1;
  }

  decrease() {
    this.count -= 1;
  }
}

export default Counter;

React.Context Stores

React.Context 可以很简单的传递 Stores

stores/index.ts:

import React from 'react';

import Counter from './Counter';
import Themes from './Themes';

const stores = React.createContext({
  counter: new Counter(),
  themes: new Themes(),
});

export default stores;

创建一个 useStoresHook,简化调用。

hooks/useStores.ts:

import React from 'react';
import stores from '../stores';

const useStores = () => React.useContext(stores);

export default useStores;

Pane 组件,使用 Stores

组件用 observer 包装,useStores 引用 stores

Pane.tsx:

import React from 'react';
import { Row, Col, Button, Select } from 'antd';
import { PlusOutlined, MinusOutlined } from '@ant-design/icons';
import { observer } from 'mobx-react-lite';

import useStores from './hooks/useStores';

type PaneProps = React.HTMLProps<HTMLDivElement> & {
  name?: string;
}

const Pane: React.FC<PaneProps> = ({ name, ...props }) => {
  const stores = useStores();

  return (
    <div {...props}>
      {name && <h2>{name}</h2>}
      <Row align="middle">
        <Col span="4">Count</Col>
        <Col span="4">{stores.counter.count}</Col>
        <Col>
          <Button
            type="text"
            icon={<PlusOutlined />}
            onClick={() => stores.counter.increase()}
          />
          <Button
            type="text"
            icon={<MinusOutlined />}
            onClick={() => stores.counter.decrease()}
          />
        </Col>
      </Row>
      {/* ... */}
    </div>
  );
};

Pane.defaultProps = { name: undefined };

export default observer(Pane);

mobx-react 与 React.Component

定义 Data Stores

makeObservable + decorators

装饰器在 MobX 6 中放弃了,但还可使用。

首先,启用装饰器语法TypeScripttsconfig.json 里启用:

"experimentalDecorators": true,
"useDefineForClassFields": true,

定义数据存储模型后,于构造函数里调用 makeObservable(this)。在 MobX 6 前不需要,但现在为了装饰器的兼容性必须调用。

stores/Counter.ts:

import { makeObservable, observable, action } from 'mobx';

class Counter {
  @observable count = 0;

  constructor() {
    makeObservable(this);
  }

  @action
  increase() {
    this.count += 1;
  }

  @action
  decrease() {
    this.count -= 1;
  }
}

export default Counter;

Root Stores

组合多个 Stores

stores/index.ts:

import Counter from './Counter';
import Themes from './Themes';

export interface Stores {
  counter: Counter;
  themes: Themes;
}

const stores : Stores = {
  counter: new Counter(),
  themes: new Themes(),
};

export default stores;

父组件,提供 Stores

父组件添加 mobx-react.Provider,并且属性扩展 stores

index.tsx:

import React from 'react';
import { Provider } from 'mobx-react';
import stores from './stores';

import Pane from './Pane';

const MobXCLS: React.FC = () => (
  <div>
    <Provider {...stores}>
      <h1>MobX with React.Component</h1>
      <div style={{ display: 'flex' }}>
        <Pane name="Pane 1" style={{ flex: 'auto' }} />
        <Pane name="Pane 2" style={{ flex: 'auto' }} />
      </div>
    </Provider>
  </div>
);

export default MobXCLS;

Pane 组件,注入 Stores

组件用 observer 装饰,同时 inject 注入 stores

Pane.tsx:

import React from 'react';
import { Row, Col, Button, Select } from 'antd';
import { PlusOutlined, MinusOutlined } from '@ant-design/icons';
import { observer, inject } from 'mobx-react';

import { Stores } from './stores';

type PaneProps = React.HTMLProps<HTMLDivElement> & {
  name?: string;
};

@inject('counter', 'themes')
@observer
class Pane extends React.Component<PaneProps, unknown> {
  get injected() {
    return this.props as (PaneProps & Stores);
  }

  render() {
    const { name, ...props } = this.props;
    const { counter, themes } = this.injected;

    return (
      <div {...props}>
        {name && <h2>{name}</h2>}
        <Row align="middle">
          <Col span="4">Count</Col>
          <Col span="4">{counter.count}</Col>
          <Col>
            <Button
              type="text"
              icon={<PlusOutlined />}
              onClick={() => counter.increase()}
            />
            <Button
              type="text"
              icon={<MinusOutlined />}
              onClick={() => counter.decrease()}
            />
          </Col>
        </Row>
        <Row align="middle">
          <Col span="4">Theme</Col>
          <Col span="4">{themes.currentTheme}</Col>
          <Col>
            <Select
              style={{ width: '60px' }}
              value={themes.currentTheme}
              showArrow={false}
              onSelect={(v) => themes.setTheme(v)}
            >
              {themes.themes.map((t) => (
                <Select.Option key={t} value={t}>
                  {t}
                </Select.Option>
              ))}
            </Select>
          </Col>
        </Row>
      </div>
    );
  }
}

export default Pane;

最后

MobX 文档可以浏览一遍,了解有哪些内容。未涉及的核心概念还有 Computeds, Reactions

其中 MobX and React 一节,详解了于 React 中的用法及注意点,见:React 集成React 优化

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