问一下数据模型中调用数据表字段的方法，谢谢~

class Video extends Model
{
    //use SoftDeletes; //软删除
    protected $fillable = ['id', 'doid', 'vid','video_url','video_cover','video_width','video_height','video_size']; //白名单

    protected $table = 'pre_home_doing_video';

    protected $primaryKey = 'doid';

在Video模型中，要调用数据表里边的字段vid
就是在下边代码里边， $videoId = 要等于vid字段的数据，要怎么写？测试了几次都有问题，麻烦大家啦。

    public function getPlayUrlAttribute(){

        //使用
        $access_key_id = "XXX";
        $access_key_secret = "XXX";
        $region_id = "cn-shanghai";

        try{
            $profile = DefaultProfile::getProfile($region_id,$access_key_id,$access_key_secret);
            $client = new DefaultAcsClient($profile);

            $videoId = " ";
            $req = new GetPlayInfoRequest();
            $req->setVideoId($videoId);
            $req->setAcceptFormat("JSON");
            $response = $client->getAcsResponse($req);

            $list = collect($response->PlayInfoList->PlayInfo)->keyBy('Format');
        }catch (Exception $e){
            exit($e);
        }

        return $list;

    }