Question

I’ve been trying to edit the getAddressesHtmlSelect() function (found in code/core/Mage/Checkout/Block/Onepage/abstract.php) in order to enable the “new address” to display first in the dropdpown created.

I’ve located the place it needs to be changed in, but I can’t figure out how to do that. Can anyone help? The code in question is:

$select = $this->getLayout()->createBlock('core/html_select')
            ->setName($type.'_address_id')
            ->setId($type.'-address-select')
            ->setClass('address-select')
            ->setExtraParams('onchange="'.$type.'.newAddress(!this.value)"')
            ->setValue($addressId)
            ->setOptions($options);

        $select->addOption('', Mage::helper('checkout')->__('New Address'));

        return $select->getHtml();

Answer 1

Look for magento block rewrite.
You need to rewrite Mage_Checkout_Block_Onepage_Billing and Mage_Checkout_Block_Onepage_Shipping
Just rewrite this blocks in your custom module and define new logic for getAddressesHtmlSelect
function

To set “New address” as default one:
Assembled working sample for you.

array_unshift($options, array('value' => '', 'label'=> Mage::helper('checkout')->__('New Address')));
            $select = $this->getLayout()->createBlock('core/html_select')
                ->setName($type.'_address_id')
                ->setId($type.'-address-select')
                ->setClass('address-select')
                ->setExtraParams('onchange="'.$type.'.newAddress(!this.value)"')
                ->setOptions($options);

            return $select->getHtml();