前端数据流之mobx-知识点

兼容性
ie11及以下，mobx4；ie11以上，mobx5（es6 Proxies）
核心思想
源自应用状态的东西都应自动获得

初始化

1. create-react-app创建项目
2. yarn add -D react-app-rewired customize-cra @babel/plugin-proposal-decorators装包
3. config-overrides.js改配置

const { override, addDecoratorsLegacy } = require("customize-cra")

module.exports = override(
  addDecoratorsLegacy()
)

4. package.json改配置
   react-scripts改成react-app-rewired
5. yarn start启动项目

mobx起步 - 计数器

安装包yarn add mobx mobx-react
index.js

import React, { Component }  from 'react';
import ReactDOM from 'react-dom';
import { observable, action} from 'mobx'
import {observer} from 'mobx-react'

// 1.初始化mobx
class store {
  @observable num = 0
  @action.bound add () {
    this.num ++
  }
}
// 2.使用mobx
@observer
class App extends Component {
  render() {
    const { store } = this.props
    return (
      <div>
        <h1>app components</h1>
        <p>{store.num}</p>
        <button onClick={store.add}>加一呀</button>
      </div>
    );
  }
}
// 3. 修改容器状态
ReactDOM.render(<App store={new store()} />, document.getElementById('root'));

装饰器

对类进行处理的函数，接收的参数就是类。

@fn1
@fn2(20)
@fn3
class TestClass {
  @readonly msg = 'hello fxd' // 只能读
}
function fn1(target) {
 target.foo = 'foo'
}
function fn2(value) {
  return function (target) {
    target.count = value
  }
}
function fn3(target) {
  target.prototype.name = 'fxd'
}
// target-目标类的prototype name-类成员名 descriptor-描述对象
function readonly(target, name, descriptor) {
  descriptor.writable = false 
}
console.log(TestClass.foo)
console.log(TestClass.count)
console.log(new TestClass().name)
console.log(new TestClass().msg)

observable

观察数据变化的方法

import { observable, action, autorun} from 'mobx'

在计算器案例中，render里面加上

    autorun( () => {
      console.log(store.num)
    })

结果为

因此，autorun一上来就会执行，数据变化时也会执行

computed

计算属性

引入

import { observable, action, computed} from 'mobx'

计算

class store {
  @observable num = 0
  @observable price = 0.5
  @computed get total () {
    console.log('我执行了')
    return this.price * this.num
  }
}

使用计算结果

<p>总金额：{store.total}元</p>

action

改变store里值的方法1：直接改变

import React, { Component }  from 'react';
import ReactDOM from 'react-dom';
import { observable } from 'mobx'
import {observer} from 'mobx-react'

class store {
  @observable num = 0
}
@observer
class App extends Component {
  render() {
    const { store } = this.props
    // 方法1.直接改变
    setTimeout(() => {
      store.num = 22
    }, 1000);
    return (
      <div>
        <h1>app components</h1>
        <p>{store.num}</p>
      </div>
    );
  }
}
ReactDOM.render(<App store={new store()} />, document.getElementById('root'));

改变store里值的方法2：使用action

import React, { Component }  from 'react';
import ReactDOM from 'react-dom';
import { observable, action, configure } from 'mobx'
import {observer} from 'mobx-react'

// 配置 - 必须通过action修改值
configure({
  enforceActions: 'observed'
})
class store {
  @observable num = 0
  // 写改变方法
  // 使用bound是为了让this永远指向容器的实例对象
  @action.bound change () {
    this.num = 22
  }
  }
}
@observer
class App extends Component {
  render() {
    const { store } = this.props
    // 方法2.用action来改变值
    setTimeout(() => {
      store.change()
    }, 1000);
    return (
      <div>
        <h1>app components</h1>
        <p>{store.num}</p>
      </div>
    );
  }
}
ReactDOM.render(<App store={new store()} />, document.getElementById('root'));

runInAction是@change的一种替代写法
引入

import { observable, action, configure, runInAction } from 'mobx'

修改方法

@observer
class App extends Component {
  render() {
    const { store } = this.props
    // runInAction来改变值
    setTimeout(() => {
      runInAction(() => {
        store.num = 33
      })
    }, 1000);
    return (
      <div>
        <h1>app components</h1>
        <p>{store.num}</p>
      </div>
    );
  }
}

异步action
有三种修改方法

1. 定义 acion函数，业务逻辑复杂推荐使用
2. 直接调用acion函数，原理和1类似，麻烦，不推荐使用
3. runInAction，业务逻辑简单时使用

import React, { Component }  from 'react';
import ReactDOM from 'react-dom';
import { observable, action, configure, runInAction } from 'mobx'
import {observer} from 'mobx-react'

configure({
  enforceActions: 'observed'
})
class store {
  @observable num = 0
  @action.bound asyncChange () {
    setTimeout(() => {
      // 方法1.定义acion函数
      // this.changeNum()
      // 方法2.直接调用action函数
      // action('changeNum', () => {
      //   this.num = 44
      // })()
      // 方法3.runInAction
      runInAction(() => {
        this.num = 55
      })
    }, 1000);
  }

  @action.bound changeNum () {
    this.num = 33
  }
}
@observer
class App extends Component {
  render() {
    const { store } = this.props
    store.asyncChange()
    return (
      <div>
        <h1>app components</h1>
        <p>{store.num}</p>
      </div>
    );
  }
}
ReactDOM.render(<App store={new store()} />, document.getElementById('root'));

数据监测

• autorun
  一上来就执行，数据改变时执行

import React, { Component }  from 'react';
import ReactDOM from 'react-dom';
import { observable, action, configure, autorun } from 'mobx'
import {observer} from 'mobx-react'

configure({
  enforceActions: 'observed'
})
class store {
  @observable num = 0
  @action.bound changeNum () {
    this.num = 22
  }
}

@observer
class App extends Component {
  render() {
    const { store } = this.props
    store.changeNum()
    // 数据监测
    autorun(() => {
      console.log('autorun=>', store.num)
    })
    return (
      <div>
        <h1>app components</h1>
        <p>{store.num}</p>
      </div>
    );
  }
}
ReactDOM.render(<App store={new store()} />, document.getElementById('root'));

• when
  如果满足执行条件，一上来就执行，数据改变时执行
  只执行一次，有执行条件

import { observable, action, configure, when } from 'mobx'

    // 数据监测
    when(
      () => {
        return store.num > 100
      },
      () => {
        console.log('when=>', store.num)
      }
    )

• reaction
  只有被监测数据改变时执行，会频繁执行

import { observable, action, configure, reaction } from 'mobx'

    // 数据监测
    reaction(
      () => {
        return store.num > 100
      },
      (data, reaction) => {
        if (data) {
          console.log('reaction=>', data)
          // 手动停止当前reaction的监听
          reaction.dispose()
        }
      }
    )