React ------ redux的安装及基础使用流程（带案例）

redux

redux也是一个架构思维， 在这个架构思维中 React 充当是 视图 V

redux使用流程 ( todolist – 增加一条数据 )

1.redux是一个架构思维，我们实现需要一个工具，这个工具叫做redux
2.安装redux

$ yarn add redux

3.在src下新建一个store,store中新建index.js用来打造store

  import { createStore } from 'redux'
  import reducer from './reducer'

  const store = createStore( reducer ) // 不加new   createStore() 参数不是一个 Object 而是一个Function

  export default store 

4.在store下新建一个state

  const state = {
    todos: [
      {
        id: 1,
        task: '任务一'
      }
    ]
  }
  export default state

5.在 store下新建一个 reducer

  import state from './state'
  const reducer = ( previousState = state , action ) => {
    const newState = {
      ...previousState           // 解构的原因是为了做深拷贝，我们操作newState，不会影响state
    }
    return newState
  }

  export default reducer 

6.在你想要使用的组件中直接引用 store

    import React, { Component,Fragment } from 'react'

    import store from '../store'

    class Content extends Component{

      constructor () {
        super()
        this.state = {
          todos: store.getState()
        }
      }

      render () {
        return (
          <Fragment>
            <div>
              <ul>
                <li> 1 </li>
              </ul>
            </div>
          </Fragment>
        )
      }

    }

    export default Content 

7.进行用户交互 React component — > actionCreators

8.在store下新建 actionCreators.js

import * as type from './type'
import store from './index'

const actionCreators = {
  add_todos_item ( val ) {
    //动作的创建

    const action = {
      type: type.ADD_TODOS_ITEM,
      payload: val // 负载数据
    }

    // 动作的发送
    store.dispatch( action )
  }
}


export default actionCreators

9.在Button组件中触发 actionCreators中 的方法

    import React, { Component,Fragment } from 'react'
    import actionCreators from './../store/actionCreators';

    class Button extends Component{

      add = () => {
        let val = this.input.value
        actionCreators.add_todos_item( val )
        this.input.value = ''
      }

      render () {
        return (
          <Fragment>
            <div>
              <input type = "text" ref = { el => this.input = el } />
              <br/>
              <button onClick = { this.add }> + </button>
            </div>
          </Fragment>
        )
      }

    }

    export default Button 

10.在 reducer中修改数据

  import state from './state'

  // const state = require( './state' )

  import * as type from './type'

  const reducer = ( previousState = state,action) => {
    let newState = {
      ...previousState
    }

    //判断用户进行了那个用户交互 ，操作新状态

    switch ( action.type ) {
      case type.ADD_TODOS_ITEM:

        //修改新状态
        newState.todos.push({
          id: newState.todos.length + 1,
          task: action.payload
        })
        
        break;
    
      default:
        break;
    }

  
    

    return newState
  }


  export default reducer 

11.进行数据个更新，通过store的订阅功能进行更新，也就是组件需要重新赋值一次数据

12.在Content组件中进行订阅

 componentDidMount () {
   store.subscribe( () => {
     this.setState({
       todos: store.getState().todos
     })
   })
 }