How to set the default option in existing dropdown attribute

Question

How do I set an option in a dropdown attribute as the default? I am adding the options to an existing attribute with this code where $aName is an array of names.

$installer = new Mage_Eav_Model_Entity_Setup('core_setup');
$installer->startSetup();
$aName = array("Name1", "Name2");

$aOption = array();
$aOption['attribute_id'] = $attr_id; 

for($iCount=1;$iCount<sizeof($aName);$iCount++){
        $aOption['value']['option'.$iCount][0] = $aName[$iCount];   
        $aOption['order']['option'.$iCount] = $iCount   ;  
}

$installer->addAttributeOption($aOption);
$installer->endSetup();

I think the answer is in Stackoverflow here but I don't know how to apply it. In my case the Attribute exists, I'm just updating the option list and setting the default.

Answer 1

You are using method addAttributeOption($option)

Such method consist following row:

            if (!isset($values[0])) {
                Mage::throwException(Mage::helper('eav')->__('Default option value is not defined'));
            }

All appearances the default value will be in $values[0]. Try to look through this method. Most probably you will find more interesting things

Answer 2

As pointed out by @zhartaunik, you can designate the first option as the default. Another way is to set the default_value in the table eav_attribute:

$attribute = Mage::getModel('eav/attribute')->load($attr_id);
$attribute->setDefaultValue($default);
$attribute->save();