element-ui的upload组件的clearFiles方法的调用

element-ui使用中碰到的问题

<template>
    <div>
        <el-button @click="clearFiles">重新上传</el-button>
        <el-upload ref="my-upload">
            <el-button type="primary">点击上传</el-button>
        </el-upload>
    </div>
</template>
<script>
    export default {
        data(){
            return {

            }
        },
        methods: {
            clearFiles () {
                this.$refs['my-upload'].clearFiles();
            }
        }
    };
</script>