get child category from flat data

Fatal error: Call to undefined method Mage_Catalog_Model_Resource_Category_Flat_Collection::joinUrlRewrite() 

This happens because the category model (catalog/category) uses different resource models for different settings of Use Flat Catalog Category and you are always using

 

 

try changing joinUrlRewrite to addUrlRewriteToResult

 

    protected function _getChildrenCategoriesBase($category)
    {
    	$collection = $category->getCollection();
    
    	$collection->addAttributeToSelect('url_key')
    	->addAttributeToSelect('name')
    	->addAttributeToSelect('all_children')
    	->addAttributeToSelect('is_anchor')
    	->addAttributeToSelect('category_code')
    	->setOrder('position', Varien_Db_Select::SQL_ASC)
    	->addUrlRewriteToResult();
    
    	return $collection;
    }
    
    public function getChildrenCategories($category)
    {
    	 
    	$collection = $this->_getChildrenCategoriesBase($category);
    	$collection->addAttributeToFilter('is_active', 1)
    	->addIdFilter($category->getChildren())
    	->load();
    	return $collection;
    }