tp5.1动态获取器 增加一个不存在的字段

$list   =   $this->agent->where($where)
            ->withAttr('region',function ($value,$data){
                $provice_name   =   regionIdToName($data['province_id']);
                $city_name      =   regionIdToName($data['city_id']);
                $county_name    =   regionIdToName($data['county_id']);
                $stree_name     =   regionIdToName($data['stree_id']);
                return $provice_name .= empty($city_name)?'':' - '.$city_name
                            .= empty($county_name)?'':' - '.$county_name
                            .= empty($stree_name)?'':' - '.$stree_name;
            })
            ->append(['region'])
            ->page($page)
            ->limit($limit)
            ->select();