Vue资源在项目中无法识别

Question

我在index.js中使用vue-resource，并且我已经安装了软件包。但是$ http.get无法正常工作。

import Vue from 'vue'
import Router from 'vue-router'
import VueResource from 'vue-resource'
import HelloWorld from '@/components/HelloWorld'

Vue.use(VueResource)
Vue.use(Router)

export default new Router({
 routes: [
  { 
   path: '/',
   name: 'HelloWorld',
   component: HelloWorld
 }
]})

HelloWorld.vue

created: () => {
  console.log('run');
  this.$http.get('https://jsonplaceholder.typicode.com/posts')
    .then((response) => {
      this.posts = response.data;
      console.log(this.newUser);
    });
}