import Vue from 'vue'
import Vuex from 'vuex'

//使用vuex模塊
Vue.use(Vuex);

//聲明靜態常量為4
const state = {
 count : 4
};

const mutations = {
 add(state,n){
 state.count +=n.a;
 },
 sub(state){
 state.count--;
 }
};

const actions = {
 //2種書寫方式
 addplus(context){ //可以理解為代表了整個的context
 context.commit('add',{a:10}) 
 },
 subplus({commit}){
 commit('sub');
 }
};

//導出一個模塊
export default new Vuex.Store({
 state,
 mutations,
 actions
})

<template>
 <div id="app">
 <div id="appaaa">
 <h1>這是vuex的示例</h1>

 <p>組件內部count{{count}}</p>
 <p>
 <button @click = "addplus">+</button>
 <button @click = "subplus">-</button>
 </p>
 </p>

 </div>
 </div>
</template>

<script>
//引入mapGetters 
import {mapState,mapMutations,mapGetters,mapActions} from 'vuex'
export default {
 name:'app',
 data(){
 return {
 
 }
 },
 computed:{
 ...mapState([
 "count"
 ]),
 },
 methods:{
 ...mapActions([
 "addplus",
 "subplus"
 ])
 }

}
</script>

<style>

</style>