父组件是列表，子组件是弹窗。通过列表插槽的查看详情打开弹窗，点击a链接查看附件，跳到新页面查看pdf等网页文件

        <a :href="attachUrl" :target="targetUrl" @click="checkAttach()">查看附件</a>

 attachUrl: '#',
 targetUrl: null,

在点击查看详情，子组件获取列表当前行数据的方法中

 add(certifyData) {
  
      this.visible = true
     this.DataHistoryId = this.$parent.DataHistoryId//获取参数
      this.execution_id = certifyData.execution_id//获取参数
      this.attachUrl = '#'
      this.targetUrl = null
      let form = {
        DataId: this.DataHistoryId,
       ItemId: this.execution_id
      }
      getHistoryAttach(form).then(res => {
        if (res.length !== 0) {
          this.attachUrl = res[0].fVcPreviewUrl
          this.targetUrl = '_blank'
        }
      })
    },

checkAttach() {
      if (this.attachUrl == '#') {
        this.$message.warning('暂无附件')
      }
    }