Cannot read property 'post' of undefined vue

Thanks for reading my question.

I have read about my problem

VUE JS 2 + WEBPACK Cannot read property 'get' of undefined VUE RESOURCE

But my system no read Vue var :(

I have a vue component calls app.vue and i need to use vue-resource to get data from my post. But the error a lot times is:

TypeError: Cannot read property 'post' of undefined
at VueComponent.loadingProcess

Do u have ideas to solve it?

My app.vue

<script>
    var Vue = require('vue');
    //Vue.use(require('vue-resource'));
    //Vue.use();

    export default {
          data () {
                return {
                    msg: 'Hello from vue-loader! nice!',
                    user: {}
            }
    },
    mounted: function () {
        this.loadingProcess();
    },
    methods: {
        loadingProcess: function () {
          
            var urlPost;
            var answQSend = {...};
            var that = this;

            var jsonSend = {
                "form_data": answQSend,
                "prod_id": 3
            };

            Vue.$http.post(urlPost, jsonSend, {
                "headers": {
                    "content-type": "application/json"
                }
            })
            .then(function(response) {

            })
            ...

First of all, thanks to @Bert who was patient and helped me find the solution

In my main.js, i changed this line

var VueResource = require('vue-resource');

for

import VueResource from "vue-resource"

and use

Vue.use(VueResource);

Then, in my app vue component i changed

Vue.http.post

For

this.$http.post

That way we fixed the error!