public function update(SubCategory $subCategory)
 {
     $id = $subCategory->getid();
     $description = $this->db > quote($subCategory->getDescription());
     $name = $this->db > quote(${$subCategory}->getName());
     $image = $this->db > quote($subCategory->getImage());
     $query = "UPDATE subcategory SET name=" . $name . " description=" . $description . " image=" . $image . " WHERE id=" . $id;
     $res = $this->db->query($query);
     if ($res) {
         return $this->findById($id);
     } else {
         throw new Exception("internal server error");
     }
 }