Vuex anybody? "TypeError: this.$store.commit is not a function"

Yeah I'm trying to work my way through the Vuex documentation slowly, building up and refactoring as I go along. I'm a little stuck with setting some user state on the Vuex store from a components ready method so it can be accessed from other components. It's all pretty basic but I can't seem to get it to work hrrmm. Any help appreciated!

// app.js

require('./bootstrap');
require('vue-resource');

import Vue from 'vue';
import Vuex from 'vuex';
import App from './components/App.vue';
import store from './vuex/store';

const app = new Vue({
    store,
    el: 'body',

    components: { 
        App
    }
});

// store.js
import Vue from 'vue';
import Vuex from 'vuex';

Vue.use(Vuex)

const store = new Vuex.Store({

    state: {
        user: {}
    },

    getters: {
        getUser: state => {
            return state.user
        }
    },

    mutations: {
        setUser(state, user) {
            state.user = user
        }
    },

    actions: {
        setUser(context) {
            context.commit('setUser')
        }

// App.vue
<template>
    <div id="app">
    </div>
</template>

<script>
import { mapState } from 'vuex'

export default {
    computed: mapState({
        user: state => state.user
    }),

    ready() {
        this.$resource('/api/user/').get({}).then(function(response){

        // Ajax call working    
        console.log(response.data);

        // None of the below work: "TypeError: this.$store.commit is not a function"

        // this.store.commit('setUser', response.data)
        // this.store.dispatch('setUser', response.data)
        // this.$store.dispatch('setUser', response.data)
        this.$store.commit('setUser', response.data)
    })}
}
</script>