在 vue 使用 el-upload 组件时，需要在上传一张图片后隐藏上传按钮
亲测可用，实现方式如下：

<el-row v-for="(item,index) in form" :key="index">
	<el-upload
	    :class="{hideUpload:form[index].img_url != ''}"
	    :limit="1" 
		name="upload_img"
		:file-list="form[index].img_url?[{name: 'upload_img', url: form[index].img_url}]:[]"
      
	    ...
	></el-upload>
</el-row>

<el-upload
    :class="{hideUpload:updata.img_url != ''}"
    :limit="1"
	name="upload_img"
	:file-list="updata.img_url?[{name: 'upload_img', url: updata.img_url}]:[]"
     
    ...
></el-upload>
...

<style lang="scss" scoped>
    .hideUpload /deep/ .el-upload{
        display:none;   /* 上传按钮隐藏 */
    }
    /* 修改 el-upload 组件大小 */
    /deep/ .el-upload{
        width: 80px;
        height: 80px;
        line-height: 80px;
    }
    /deep/ .el-upload-list--picture-card .el-upload-list__item{
        width: 80px;
        height: 80px;
        line-height: 80px;
    }
</style>