Magento Products Compare limit

Question

I want to set a max amount of products that can be added to the compare list. I want to set the max at 3 products that can be compare.

Tried this code:

Step1:Create config.xml at app>code>local>Stackexchange>Magento38261>etc

Code:

<?xml version="1.0" ?>
<config>
    <modules>
        <Stackexchange_Magento38261>
            <version>1.0.0</version>
        </Stackexchange_Magento38261>
    </modules>

    <global>
        <models>
            <magento38261>
                <class>Stackexchange_Magento38261_Model</class>
            </magento38261>
        </models>
    </global>
    <frontend>
        <events>
            <controller_action_predispatch_catalog_product_compare_add>
                <observers>
                    <prevent_add_to_compare>
                        <class>magento38261/observer</class>
                        <method>preventadd</method>
                    </prevent_add_to_compare>
                </observers>
            </controller_action_predispatch_catalog_product_compare_add>
        </events>
    </frontend>
</config>

Step2: create Observer.php at app>code>local>Stackexchange>Magento38261>Helper

Code:

<?php
class Stackexchange_Magento38261_Model_Observer{
    public function preventadd($observer){

          $controller = $observer->getControllerAction();

         $items=Mage::getResourceModel('catalog/product_compare_item_collection')
                ->useProductItem(true)
                ->setStoreId(Mage::app()->getStore()->getId());
             if (Mage::getSingleton('customer/session')->isLoggedIn()) {
            $items->setCustomerId(Mage::getSingleton('customer/session')->getCustomerId());
            }else {
            $items->setVisitorId(Mage::getSingleton('log/visitor')->getId());
            }
            /* send error */
            if(count($items)>3){
             Mage::getSingleton('catalog/session')->addError(Mage::helper('catalog')->__('Error.'));
            $controller->setFlag('', Mage_Core_Controller_Varien_Action::FLAG_NO_DISPATCH, true);
           // $controller->getResponse()->setRedirect(Mage::getUrl());

            /* start to redirec to lst page */
            $refererUrl = Mage::app()->getRequest()->getServer('HTTP_REFERER');
            if ($url = Mage::app()->getRequest()->getParam('referer_url')) {
                $refererUrl = $url;
            }
            if ($url =Mage::app()->getRequest()->getParam('r64')) {
                $refererUrl = Mage::helper('core')->urlDecode($url);
            }
            if ($url =Mage::app()->getRequest()->getParam('uenc')) {
                $refererUrl = Mage::helper('core')->urlDecode($url);
            }


            if (empty($refererUrl)) {
                $refererUrl =Mage::getBaseUrl();
            }
             $controller->getResponse()->setRedirect($refererUrl);

            }


            return $this;

    }
}

Step3:module file Stackexchange_Magento38261.xml at app\etc\modules

code:

<?xml version="1.0" ?>
<config>
    <modules>
        <Stackexchange_Magento38261>
            <codePool>local</codePool>
            <active>true</active>
        </Stackexchange_Magento38261>
    </modules>
</config>

But this code does not work, because I still can add more than 3 products to the compare list.

Answer 1

The controller_action_predispatch_catalog_product_compare_add event is triggered before the action is executed.

So to check the item count at that point you have to use count($items) + $itemCountToBeAdded, where $itemCountToBeAdded is based on the request (how many products is the user trying to add)

Also it is not enough to set a redirection, you also have to tell Magento not to execute the action:

$controller->setFlag('', Mage_Core_Controller_Front_Action::FLAG_NO_DISPATCH, true);