Add a restriction to the product model

Question

I have a situation and I'm not sure what the best solution is.

In the user accounts (customers) I've added a single field that gives a list of all the manufacturers. The admin can select a set of manufacturers per customer.

When a customer logs in on the frontend, he should only be able to see the product of the manufacturers that are selected.

I was thinking of rewriting some pieces of the product model, but I'm not sure what would be the best location, any tips?

Answer 1

There are a few ways of doing this. Personally I would suggest listening to the event catalog_product_collection_load_before. This can be done with the following section of config.xml

<events>
    <catalog_product_collection_load_before>
        <observers>
            <your_module>
                <type>singleton</type>
                <class>your_module/observer</class>
                <method>catalogProductCollectionLoadBefore</method>
            </your_module>
        </observers>
    </catalog_product_collection_load_before>
</events>

Then in your observer you should be able to add the filters that you need with something like the following.

public function catalogProductCollectionLoadBefore(Varien_Event_Observer $observer) {
    /** @var Mage_Catalog_Model_Resource_Product_Collection $collection */
    $collection = $observer->getCollection();
    $collection->addAttributeToFilter('attribute_code', array('in' => array(5,6)));

    // If you log your select then you can double check that the correct sql is being formed
    mage::log((string) $collection->getSelect());
}

Obviously you can remove the mage::log once you have the correct filters on your collection.