TypeError: Cannot read property 'data' of undefined

[kashtech79]

I try to store my login token but following error prevent storing data & produce following error
TypeError: Cannot read property 'data' of undefined

my login.vue is

export default {
data(){
return {
form:{
email: null,
password: null
}
}
},
methods:{
login(){
axios.post('/api/login',this.form)
.then(res => User.responseAfterLogin(res))
.catch(error => console.log(error.response.data))

user.js

class User{

responseAfterLogin(res){
    const access_token = res.data.access_token
    const username = res.data.name
        if (Token.isValid(access_token)) {
        AppStorage.store(access_token,username)
    }

can anyone help me on this ?