Magento Observer object not containing anything

Question

I have an observer method that triggers upon the event sales_order_creditmemo_save_after, basically when a credit memo was created. The method I have fires:

public function handleCreditmemoCreation(Varien_Event_Observer $observer)
    {
        //$observer contains data passed from when the event was triggered.
        $fp = fopen('/Applications/MAMP/htdocs/magento-1/var/log/request.log', 'a');
        fwrite($fp, $observer->getData());
        fwrite($fp, 'test');
        fclose($fp);
    }

However, $observer->getData() doesn't output anything into the request.log log file. To confirm I configured the file correctly, I write the string 'test' to the file, which works.

Also, when I check $observer for null, it tells me that $observer is not null. Does anyone know why then it does not seem to contain anything?

Answer 1

To access observer passed data you'd always use $observer->getEvent()

$observer->getEvent()->getData(XXX)

Where XXX is variable, as every event can contain different data

In your case, if you browse Mage_Sales_Model_Order_Creditmemo class, you will find this properties

protected $_eventPrefix = 'sales_order_creditmemo';
protected $_eventObject = 'creditmemo';

First of them tells us the event prefix this model will use when firing standard Magento model events. For instance: sales_order_creditmemo_save_after (yours), sales_order_creditmemo_delete_before, etc...

The second tells us the object passed in that events. So, in your concrete case, you can access creditmemo object this way...

$observer->getEvent()->getCreditmemo();
$observer->getEvent()->getData('creditmemo'); // same result