Currently there are three types of product relations in Magento: Up-sells, Related Products, and Cross-sell Products. Recently while discussing client’s requirements, we’ve come to conclusion it would would serve our purpose best to link products in the same way Magento does, and then use our own relations independently of Magento’s built in product relations. In this article I’ll show you how to add custom product relations as addition to existing Magento product relations.
Introduction
Inside following paragraphs I’ll do my best to present code snippets from Magento extension created to illustrate process of adding custom product relations in Magento. Full source code for the extension named Inchoo_CustomLinkedProducts is available from its GitHub repository page.
Installer script
First thing we need to do is notify Magento database about out new product link type. We will do this using following installer script:
app/code/community/Inchoo/CustomLinkedProducts/sql/inchoo_customlinkedproducts_setup/install-0.0.1.php
Admin interface
Next thing we need to do is rewrite adminhtml/catalog_product_edit_tabs block to add another tab to Product Information screen:
app/code/community/Inchoo/CustomLinkedProducts/Block/Adminhtml/Catalog/Product/Edit/Tabs.php
Since our tab points to ‘*/*/custom’, we need to add this route to Mage_Adminhtml_Catalog_ProductController by another rewrite. This time we’ll rewrite controller:
app/code/community/Inchoo/CustomLinkedProducts/controllers/Adminhtml/Catalog/ProductController.php
For getBlock(‘catalog.product.edit.tab.custom’) to work on both customAction() and customGridAction(), we also need to add a bit of XML to our layout:
app/design/adminhtml/default/default/layout/inchoo_customlinkedproducts.xml
Next thing, we need to create grid to be hosted inside our newly created Custom Linked Products tab. There’s a lot if code for this task, but much of it is pretty generic custom grid. The one thing you’ll notice is call to useCustomLinks() inside _prepareCollection() function. Here’s the excerpt from our grid class:
app/code/community/Inchoo/CustomLinkedProducts/Block/Adminhtml/Catalog/Product/Edit/Tab/Custom.php
So this is how interface for managing Custom Linked Products looks like inside Magento admin:
Backend supporting code
As you might have noticed, function useCustomLinks() doesn’t exist inside catalog/product_link model, thus we need to rewrite this model to include our custom product link specific functionality:
app/code/community/Inchoo/CustomLinkedProducts/Model/Catalog/Product/Link.php
If you were to add another custom relation to same Magento installation, you would need to increase LINK_TYPE_CUSTOM class constant to avoid conflicts. Now you might notice that our catalog/product model doesn’t have getCustomLinkData() function. Fear not, another rewrite to the rescue:
app/code/community/Inchoo/CustomLinkedProducts/Model/Catalog/Product.php
There’s one more crucial thing left to do. To enable our product relations save and duplicate functionality on catalog product, we must attach to catalog_product_prepare_save and catalog_model_product_duplicate events. Here’s the observer class with callbacks for these events:
Frontend interface
To demonstrate our custom product relation on Magento frontend, I’ve cloned Magento’s related products block inside inchoo_customrelatedproducts/catalog_product_list_custom block together with related template file. Our Related Products block clone will use our custom product relations instead of builtin Related Products relations. This is how it looks like in frontend:
I hope you’ll find some use for this code inside your own projects. Like always if you have any questions please leave your comment here and I’ll respond as soon as possible. If you’ve noticed some bug or wish to improve this code in any way, feel free to fork Inchoo_CustomLinkedProducts on GitHub.