uni-app 点击切换class

<view class="footer">

<view class="footer_item " @click="change_nav(index)" v-for="(item,index) in footer_nav" :key="index">

    <image :src="add_class==index?item.select_icon:item.icon" mode="" v-if="index==2"></image>

    <view :class="{'active':add_class==index}">{{item.name}}</view>

</view>

</view>

export default {

    data() {

        return {

            add_class:'',

        };

    },

    methods:{

        change_nav(index){

        this.add_class=index

    },

}