Vuex异步请求存取步骤

 --------------------------
 vuex 
 1.首先在state中创建变量
 export default {
   // 首页轮播图
   homecasual: []
 }
 2.然后在action中调用封装好的axios请求，异步接收数据，commit提交给mutation
 引入
 import {
   getHomeCasual,
 } from '../api'
 ------------------
 引入mutationtype规范---
 import {
   HOME_CASUAL,
 } from './mutation-types'
 介绍一下这里---
 在mutation-types中创建
 export const HOME_CASUAL = 'home_casual'; // 首页轮播图
 -----------------------------
export default {
  // 1. 获取首页的轮播图
  async reqHomeCasual({commit}, callback) {
    const result = await getHomeCasual();
    commit(HOME_CASUAL, {homecasual: result.message.data})
    callback && callback();
   },
  }
  ---------------
  3.在mutations中改变state中的状态
  引入规范
  import {
     HOME_CASUAL,
  } from './mutation-types'
  将从actons中获取到的值赋值给state
export default {
  [HOME_CASUAL](state, {homecasual}){
      state.homecasual = homecasual;
  },
 }