Magento – process collection after load collection

$categoryid = 43;

$layer = Mage::getModel("catalog/layer");

$category = Mage::getModel("catalog/category")->load($categoryid);

$layer->setCurrentCategory($category);

$attributes = $layer
    ->getFilterableAttributes()
    ->addDisplayInAdvancedSearchFilter()
    ;

Mage::log($attributes->getSelect());

foreach ($attributes as $attribute) {
    echo $attribute->getAttributeCode(). " ". $attribute->getStoreLabel() ."<br/>";
}

I want tho filters attributes which is used in layered navigation and used in advance search. When I print query the result query working fine but print the attribute filter they give only getFilterableAttributes.

The getFilterableAttributes method class Mage_Catalog_Model_Layer load collection first then I use addDisplayInAdvancedSearchFilter cause will effect after load collection.

I want to know is there any method load collection after loading the method. Any one face these kind of problem then please help how it works.

In class Mage_Catalog_Model_Layer method getFilterableAttributes have following code.

public function getFilterableAttributes()
    {
        $setIds = $this->_getSetIds();
        if (!$setIds) {
            return array();
        }
        /** @var $collection Mage_Catalog_Model_Resource_Product_Attribute_Collection */
        $collection = Mage::getResourceModel('catalog/product_attribute_collection');
        $collection
            ->setItemObjectClass('catalog/resource_eav_attribute')
            ->setAttributeSetFilter($setIds)
            ->addStoreLabel(Mage::app()->getStore()->getId())
            ->setOrder('position', 'ASC');
        $collection = $this->_prepareAttributeCollection($collection);
        $collection->load();

        return $collection;
    }

When I add $collection->addDisplayInAdvancedSearchFilter() before $collection->load() but its wokring fine. Like This.

public function getFilterableAttributes()
    {
        $setIds = $this->_getSetIds();
        if (!$setIds) {
            return array();
        }
        /** @var $collection Mage_Catalog_Model_Resource_Product_Attribute_Collection */
        $collection = Mage::getResourceModel('catalog/product_attribute_collection');
        $collection
            ->setItemObjectClass('catalog/resource_eav_attribute')
            ->setAttributeSetFilter($setIds)
            ->addStoreLabel(Mage::app()->getStore()->getId())
            ->setOrder('position', 'ASC');
        $collection = $this->_prepareAttributeCollection($collection);
        $collection = $this->addDisplayInAdvancedSearchFilter();
        $collection->load();

        return $collection;
    }

Its work fine.

I don't want to rewrite Mage_Catalog_Model_Layer Model.

Thanks