問大家個問題，我props傳desc對象的時候，為什么會顯示undefined呢，我明明設置了默認值<template>  <transition name="slide">    <div v-show="showFlag" class="food" ref="food">        <ratingselect v-if="desc" :desc="desc" ></ratingselect>    </div>  </transition></template><script>import ratingselect from '@/components/ratingselect/ratingselect'export default {  name: 'food',  data () {    return {      desc: {        all: '全部',        positive: '推薦',        negative: '吐槽'      }    }  },  components: {    ratingselect  }}</script><template>  <div class="ratingselect">    <div class="rating-type">      <span>{{desc.all}}</span>      <span>{{desc.positive}}</span>      <span>{{desc.negative}}</span>    </div>    <div class="swith">      <span class="icon-check_circle"></span>      <span class="text">只看有內容的評價</span>    </div>  </div></template><script>export default {  prop: {    desc: {      type: Object,      default () {        return {          all: '全部',          positive: '滿意',          negative: '不滿意'        }      }    }  },  data () {    return {    }  }}</script>