Is it possible to add new functionality to OPC method saveBilling by Observer?

Question

I need to add new customer field. This field should be available during customer registration via OPC. How I can do it? I can rewrite Mage_Checkout_Model_Type_Onepage modify method saveBilling and add into it:

$this->getCheckout()->setSomeField($data['some_field']);

After it I can call Observer on event checkout_type_onepage_save_order and use such code:

$quote = $observer->getEvent()->getQuote();
$customer = $quote->getCustomer();
$customer->setSomeField(Mage::getSingleton('checkout/session')->getSomeField());

And this field will be added to customer.

But I already have 2 time rewrites for class Mage_Checkout_Model_Type_Onepage. And this one will be third. I don't like. Maybe I can use some event for it? Or any other approach?

Answer 1

For adding a custom filed in billing step of customer registration, this might help you. For basic creation of custom customer attribute, refer this link. This process has a considerable amount of coding and that's why I'm providing the link.

And yo! you don't need to override Mage_Checkout_Model_Type_Onepage :)