Code before a controller's action is executed?

Question

I would like to write some custom code before any actions in a controller is executed. It would seem like an easy one, but i am unable to find help anywhere in google. I tried to override preDispatch() function in my controller, but it ends up getting weird (instead of showing my page, it shows the default page without any content in it)

Its a admin controller and i need to do some custom validation before any action in it is executed. Based on the validation, the request may be forwarded to some other controller.

Answer 1

Good news: there's no need to rewrite preDispatch! There is dynamic eventing that is fired both before and after the dispatch:

An excerpt of what is required to tap into the event in your module's etc/config.xml file:

<global>
    <events>
        <controller_action_predispatch_catalog_product_view>
            <observers>
                <yourmodule_capcpv>
                    <class>YourCompany_YourModule_Model_Observer</class>
                    <method>catalogProductViewPredispatch</method>
                </yourmodule_capcpv>
            </observers>
        </controller_action_predispatch_catalog_product_view>
    </events>
</global>

And your observer would look like the following:

app/code/local/YourCompany/YourModule/Model/Observer.php:

<?php

class YourCompany_YourModule_Model_Observer
{
    public function catalogProductViewPredispatch($observer)
    {
        //get the controller action method
        $controller = $observer->getEvent()->getControllerAction();

        //log something
        Mage::log('Testing - I made it to the predispatch of the catalog product viewAction!');

        //get things from the request:
        $request = $controller->getRequest();

        //set things on the response:
        $reponse = $controller->getResponse();
        $response->setBody('some stuff');
    }
}

Answer 2

here is an example of Customer->AccountController. In the controller you have override mention mention predispatch function as mentioned below:

public function preDispatch()
{
$action = $this->getRequest()->getActionName();
$ExitsopenActions = array(
'create',
'login',
'logoutsuccess',
'forgotpassword',
'forgotpasswordpost',
'changeforgotten',
'resetpassword',
'resetpasswordpost',
'confirm',
'confirmation'
);
$newOpenAction=array('passwordreset');
$allActions=array_merge($ExitsopenActions,$newOpenAction);
$Custompattern = '/^(' . implode('|', $newOpenAction) . ')/i';

if (preg_match($Custompattern, $action)) {
$this->getRequest()->setActionName('create');
}
parent::preDispatch();

if ($action != $this->getRequest()->getActionName())
{
$this->getRequest()->setActionName($action);
}
if (!$this->getRequest()->isDispatched()) {
return;
}
$mypattern = '/^(' . implode('|', $allActions) . ')/i';
if (!preg_match($mypattern, $action)) {
if (!$this->_getSession()->authenticate($this)) {
$this->setFlag('', 'no-dispatch', true);
}
} else {
$this->_getSession()->setNoReferer(true);
}
}

$ExitsopenActions consists of all the actions that are there in the native.

$newOpenAction consists of all the new actions you want to add.