/**
  * Add a Subcategory
  * 
  * @param int $category_id          internal category id
  * @param string $subcategory_name  subcategory name
  */
 public function addSubcategory($category_id, $subcategory_name)
 {
     // get category
     $category = $this->getCategoryById($category_id);
     // create subcategory
     $subcategory = new Subcategory();
     $subcategory->setName($subcategory_name);
     $subcategory->setOwner($this->owner);
     // assign subcategory to category
     $subcategory->setCategory($category);
     // update
     $this->update($subcategory);
 }
 /**
  * @param Subcategory $subcategory
  */
 public function addSubcategory(Subcategory $subcategory)
 {
     $subcategory->setCategory($this);
     $subcategory->setOwner($this->owner);
     $this->subcategories->add($subcategory);
 }