Overriding a core controller's preDispatch method

Question

I need to override a core controller's preDispatch method. The core controller inherits from Mage_Checkout_Controller_Action, which itself has a preDispatch method that needs to be called. Since I'm extending from the core controller I want to override, I cannot just call parent::preDispatch(), since that would pull in functionality that I'm trying to avoid.

My question is - How can I call an overridden method that is 2 levels higher in the inheritance chain, or am I just going about this the wrong way?

Update

Apparently this works:

Mage_Checkout_Controller_Action::preDispatch(); (even though that method is not static, I guess you learn something new every day..)

Now my question is: Is there a better way of doing this without having to copy in all functionality from the class I am overridding?

The reason I am attempting this is because I was going down this path, attempting to force Magento to remember address assignments when customers go through multishipping checkout and then subsequently leave. (FWIW, I found the linked to article great for getting me going in the right direction, but there seems to be a lot missing as far as steps that need to be taken to get this to work).

The controller I'm overriding is the core MultiShippingController which has a redirect back to the Multishipping IndexAction that needs to be avoided. On a somewhat side-note, I have gotten this functionality mostly complete, save for a few issues (relating to the adding of the first item to the cart and the Mage_Sales_Model_Quote_Item->getQuoteItem() returning null in the addresses.phtml template, though that is an entirely different discussion).

Answer 1

I think it'd be interesting to know exactly what you're trying to accomplish, but I can give you a few pointers without knowing details:

In most cases if the method you're trying to reference does not use $this, you can safely call it statically:

Mage_Checkout_Controller_Action::preDispatch()

But you should probably be doing this via a controller predispatch observer. Magento affords you the ability to do this in Mage_Core_Controller_Varien_Action:

abstract class Mage_Core_Controller_Varien_Action
{
    // [...]
    public function preDispatch()
    {
        // [...]
        if ($this->_rewrite()) {
            return; // [What is the purpose if this?]
        }
        // [...]

        // [This is where my event needs to be firing, but this code never gets 
        // executed because the controller is rewritten]
        Mage::dispatchEvent(
            'controller_action_predispatch_'.$this->getFullActionName(),
            array('controller_action'=>$this)
        );

    }
    // [...]
}

All you have to do is add the full action name onto the end of controller_action_predispatch. An example of shoehorning functionality into Onepage Savebilling:

    <events>
        <controller_action_predispatch_checkout_onepage_saveBilling>
            <observers>
                <some_unique_name_for_this_event>
                    <class>yourmodel/observer</class>
                    <method>myPredispatchObserver</method>
                </some_unique_name_for_this_event>
            </observers>
        </controller_action_predispatch_checkout_onepage_saveBilling>
    </events>

What's more, in your observer method, you need to accept the observer and you can get the controller itself from getEvent:

<?php

class MyCompany_MyModule_Model_Observer
{

    public function myPredispatchObserver($observer)
    {
        $controller = $observer->getEvent()->getControllerAction();
    }
}

Answer 2

I'm on my phone, but I'd think that you could use any one of several events to remove the redirect from the response object.