/**
  * @see	\wcf\data\category\CategoryNodeTree::buildTree()
  */
 protected function buildTree()
 {
     $categoryList = new CategoryList();
     $categoryList->getConditionBuilder()->add('category.objectTypeID = ?', array(CategoryHandler::getInstance()->getObjectTypeByName($this->objectType)->objectTypeID));
     $categoryList->readObjects();
     foreach ($categoryList as $category) {
         if (!isset($this->categoryStructureCache[$category->parentCategoryID])) {
             $this->categoryStructureCache[$category->parentCategoryID] = array();
         }
         $this->categoryStructureCache[$category->parentCategoryID][] = $category->categoryID;
         $this->categoryCache[$category->categoryID] = $category;
     }
     parent::buildTree();
 }