iview tree組件在for循環(huán)中無法使用getCheckedNodes這個方法
<div v-for="(item,index) in arr">

    <div key="index">
        <tree v-if="item===0" ref="tree" :data="data2" show-checkbox @on-check-change="tree_change"></tree>
        <div else>2313</div>
    </div>

</div>
 tree_change()
        {
          // console.log(this.$refs.tree.children);
         var nodes=this.$refs.tree.getCheckedNodes();

         console.log(nodes);
        }

報錯：
vue.js:584 [Vue warn]: Error in event handler for "on-check-change": "TypeError: this.$refs.tree.getCheckedNodes is not a function"