在vuecli中使用axios请求发送成功，获取不到返回值的问题

axios.post('http://localhost:12612/api/register', this.ruleForm)
.then((res) => {  //res为undefined
debugger
console.log(res)
})
.catch((error) => {
console.log(error)
})

Vue.prototype.$http = axios

this.$http.post('http://localhost:12612/api/register', this.ruleForm)
.then((res) => {  //res为undefined
debugger
console.log(res)
})
.catch((error) => {
console.log(error)
})

npm install vue-axios --save

import axios from 'axios'
import VueAxios from 'vue-axios'

Vue.use(VueAxios,axios)

import axios from 'axios'
import vueAxios from 'vue-axios'
.
.
.
this.axios.post('http://localhost:12612/api/register', this.ruleForm)
then((res) => {
console.log(res)
})
.catch((error) => {
console.log(error)
})