Get coupon code when invalid

Question

Which observer could I use to get the coupon code inserted by the customer when this is not valid on checkout cart page?

I tried using the salesrule_validator_process but coupon code is null when it's not valid. I'm using the following code to get it:

 $quote = Mage::getSingleton('checkout/session')->getQuote();
 $coupon_code = $quote->getData('coupon_code');

Answer 1

You need to used this event :

<config>
    <global>
        <events>
            <controller_action_postdispatch_checkout_cart_couponPost>
                <observers>
                    <coupencodevalidationobserver>
                        <type>singleton</type>
                        <class>Vendor_Extension_Model_Checkout_Observer</class>
                        <method>validatecouponcode</method>
                    </coupencodevalidationobserver>
                </observers>
            </controller_action_postdispatch_checkout_cart_couponPost>
        </events>
    </global>
</config>

And in observer file you get coupen code like this :

public function validatecouponcode(Varien_Event_Observer $observer)
{

    $controller = $observer->getControllerAction();
    $coupencode = $controller->getRequest()->getParam('coupon_code');
    // Do your logic here
    return $this;
}