Use Magento’s Core Shopping Cart Model to store/access a list of products

Question

I’m looking for an elegant way to use Magento’s Core Shopping Cart Model to store/access a list of products on a visitor/customer session WITHOUT displaying the products in the basket and WITHOUT modifying magento's core files.

Answer 1

Easy! Just add a new quote_item attribute and filter for it in the quote_item_collection. If you need more details, tell me.

You implement your own module. You add a new attribute to the quote_item.

Specifiy a setup script

<?xml version="1.0"?>
<config>
    <modules>
        <Namespace_Module>
            <version>1.0.0</version> <!-- this is the version for the install script -->
        </Namespace_Module>
    </modules>
    <global>
        <resources>
            <namespace_module_setup> <!-- this is the name of the directory in sql -->
                <setup>
                    <module>Namespace_Module</module>
                    <class>Mage_Sales_Model_Entity_Setup</class> <!-- this is important, because in newer versions (magento >1.6?) all sales entity (quote, quote_item, order, order_item, ...) are flat tables -->
                </setup>
            </namespace_module_setup>
        </resources>
    </global>
</config>

add a install script:

app/code/(local|community)/namespace/module/sql/namespace_module_setup/install-1.0.0.php
<?php
/* @var $this Mage_Eav_Model_Entity_Setup */
$this->startSetup();

$this->addAttribute(
    'quote_item',
    'hide',
    array(
         'visible_on_front' => 0,
         'type'             => 'int',
         'label'            => 'Hide in cart',
         'required'         => 0,
         'user_defined'     => 1
// other values and config settings can be seen here: /app/code/core/Mage/Eav/Model/Entity/Setup.php:592
    )
);

$this->endSetup();

Then you set the new attribute on the quote_item after you added it to the cart $quoteItem->setHide(1); it is saved automatically (clean the cache!).

And then you can use any event, e.g. eav_collection_abstract_load_before:

<frontend>
    <events>
        <eav_collection_abstract_load_before>
            <observers>
                <your_name>
                    <type>singleton</type>
                    <class>namespace_module/observer</class>
                    <method>eavCollectionAbstractLoadBefore</method>
                </your_name>
            </observers>
        </eav_collection_abstract_load_before>
    </events>
</frontend>

In this method you check whether it is a Mage_Sales_Model_Entity_Quote_Item_Collection and then you add a addAttributeToFilter('hide', 1)

then the items are not loaded.