Magento : How to add handle through observer - magento

Question

I am trying to use addHandle(), but using the following generates error:
public function HandleMe($observer)
$update = $observer->getEvent()->getLayout()->getUpdate();
$update->addHandle('handlename');
raises a "Fatal error: Call to a member function getUpdate()"

Answer 1

You have to load core/layout before you update the layout, So try follow below code,
public function addCustomHandles($observer) {
$update = Mage::getSingleton('core/layout')->getUpdate();
//Your code here..
}
Or refer below link,
Link 1
Link 2

Answer 2

try using following approach :
First add this to your config.xml in yourcustommodule:
<config>
<frontend>
<events>
<controller_action_layout_load_before>
<observers>
<yourcustomtheme_observer>
<class>yourcustomtheme/observer</class>
<method>addHandles</method>
</yourcustomtheme_observer>
</observers>
</controller_action_layout_load_before>
</events>
</frontend>
</config>
And then add following method to your observer
class YourPackage_YourCustomTheme_Model_Observer extends CLS_Core_Model_Abstract
{
public function addHandles($observer) {
$category = Mage::registry('current_category');
if ($category instanceof Mage_Catalog_Model_Category) {
$update = Mage::getSingleton('core/layout')->getUpdate();
$fertilility = (count($category->getChildrenCategories()->getData())) ? 'parent' : 'nochildren';
$update->addHandle('catalog_category_' . $fertilility);
}
return $this;
}
}
PS : this is only for reference, so that you can check whether you are correctly using observer and handles or not.