请问为什么无法往vue.prototype上挂载

Question

Loading.vue

<template>
    <div v-show="show" class="container">
        <div class="loading"></div>
    </div>
</template>

<script>
export default {
  name: "Loading",
  data() {
    return {
      show: false
    }
  }
}
</script>

index.js

import LoadingComponent from './Loading'
const Loading = {}
Loading.install = function (Vue) {
  const LoadingConstructor = Vue.extend(LoadingComponent)
  const instance = new LoadingConstructor()
  instance.$mount(document.createElement('div'))
  document.body.appendChild(instance.$el)
  Vue.prototype.$loading = {
    show() {
      instance.show = true
    },
    close(){
      instance.show = false
    }
  }
}
export default Loading

main.js

import Loading from './components/loading/index.js'

Vue.use(Loading)

Vue.prototype上没有成功挂载到$loading，请问这是为什么

Answer 1

在 index.js 中引入 vue

import vue from 'vue'