When building custom modules for Magento, one of the most common needs is to override Magento’s core files, most commonly Blocks, Models, Resources, and Controllers. And, by the way, when I say “override”, that is also synonymous with “rewrite” or “extend”.
I wanted to write this up for my own reference, but I hope this ends up helping you to. At the time of writing this, all of these methods have been tested on 1.4.0. This post assumes you to have familiarity with writing Magento modules. And remember, you only need to include functions in your file that you are modifying. Leave all untouched functions out of your file.
Also, the reason I haven’t included much for examples of the actual block/model code is that 90% of getting a rewrite to work correctly is just getting your config.xml correct. It matters way less of where you put your files in your module (though it’s good to keep it organized and clean).
Overriding Core Blocks
One of the more simple and straight-forward things to override in Magento. Let’s say that you want to override the following class: Mage_Catalog_Block_Product_View.
The first step is to copy the file into your own module’s Block folder. It can be anywhere you want within that folder, it really doesn’t matter. But, for organizational purposes, it’s always best, in my opinion, to keep a similar folder/file structure as Magento does. In this case, I would put this file in My/Module/Block/Catalog/Product/View.php. Of course, you’ll need to rename the class, and have it extend Mage_Catalog_Block_Product_View.
Here is how the ‘blocks’ tag in your config.xml should look:
<blocks> <my_module> <class>My_Module_Block</class> </my_module> <catalog> <rewrite> <product_view>My_Module_Block_Catalog_Product_View</product_view> </rewrite> </catalog> </blocks>
As you can see, we’ve got the rewrite xml inside of the ‘catalog’ tag. This refers to app/code/core/Mage/Catalog/. Then the ‘rewrite’ tag tells Magento that we are going to override a block (since we are within the ‘blocks’ tag) under Mage/Catalog/. The ‘product_view’ tag points to Mage/Catalog/Block/Product/View.php, and within that tag is the name of the class that we are using to override the core block.
As another example, if you wanted to override Mage/Catalog/Block/Product/View/Type/Simple.php, the tag under ‘rewrite’ would be ‘product_view_type_simple’.
Overriding Core Models
Overriding models (but not resource models, which are anything declared in config.xml as ‘resourceModel’, which are typically files within a Mysql4 directory) is basically the same as blocks (above). So, I will give an example, but leave out much of the explanation.
Lets say that I want to modify the model for the items on an order invoice (Mage_Sales_Model_Order_Invoice_Item). I will copy that file to My/Module/Model/Sales/Order/Invoice/Item.php, rename the class, and extend Mage_Sales_Model_Order_Invoice_Item.
The config.xml ‘models’ will look something like this:
<models> <my_module> <class>My_Module_Model</class> </my_module> <sales> <rewrite> <order_invoice_item>My_Module_Block_Sales_Order_Invoice_Item</order_invoice_item> </rewrite> </sales> </models>
Overriding Core Resource Models
I found out the hard way once, and wasted a couple hours, that resource models have a different way of overriding them. All of the concepts are the same, with the exception of the syntax in your config.xml file. A resource model is typically going to be models that reside within a ‘Mysql4′ folder. The resource model folder is typically defined in the config.xml file using the tag ‘resourceModel’.
I was putting together a dependent filter module, and I needed to override this class: Mage_Catalog_Model_Resource_Eav_Mysql4_Attribute. Just as the above examples, I created this file: My/Module/Model/Catalog/Resource/Eav/Mysql4/Attribute.php, renamed the class, and extended Mage_Catalog_Model_Resource_Eav_Mysql4_Attribute.
As I said above, the xml syntax changes for resource models. Instead of defining just the ‘catalog’ tag right before the ‘rewrite’, you actually have to define all the way down to the mysql4 folder. Here is an example for the above model:
<models> <my_module> <class>My_Module_Model</class> </my_module> <catalog_resource_eav_mysql4> <rewrite> <attribute>My_Module_Model_Catalog_Resource_Eav_Mysql4_Attribute</attribute> </rewrite> </catalog_resource_eav_mysql4> </models>
Overriding Admin Core Controllers
I have seen numerous methods on how to do this, but the method I will describe seems to be the current ‘standard’.
Lets say that I need to override the adminhtml attribute controller: Mage_Adminhtml_Catalog_Product_AttributeController. First thing is to create the controller in your module. I would put mine in My/Module/controllers/Catalog/Product/AtttributeController.php. An important key to note here is that with controllers, Magento does not autoload them like it does with blocks and models. So, we’ll need to include the file of the controller that we want to override. Here is an example of how my controller would look:
<?php include_once("Mage/Adminhtml/controllers/Catalog/Product/AttributeController.php"); class My_Module_Catalog_Product_AttributeController extends Mage_Adminhtml_Catalog_Product_AttributeController { ...
The config.xml file is key now. Unlike models and blocks, you don’t need to define exactly which/where controller you are needing to override. You just need to define whether it is an ‘admin’ or ‘frontend’ controller, which module has the controller(s) you are overriding, and which module you are overriding it with (your own, obviously).
Here is the example for the above controller:
<config> <admin> <routers> <adminhtml> <args> <modules> <my_Module before="Mage_Adminhtml">My_Module</my_Module> </modules> </args> </adminhtml> </routers> </admin> </config>
Overriding Frontend Core Controllers
Lets override the Onepage Checkout controller: Mage_Checkout_OnepageController. First thing is to create the controller in your module. I would put mine in My/Module/controllers/Checkout/OnepageController.php. An important key to note here is that with controllers, Magento does not autoload them like it does with blocks and models. So, we’ll need to include the file of the controller that we want to override. Here is an example of how my controller would look:
<?php include_once('Mage/Checkout/controllers/OnepageController.php'); class My_Module_Checkout_OnepageController extends Mage_Checkout_OnepageController { ...
The config.xml file is key now. Unlike models and blocks, you don’t need to define exactly which/where controller you are needing to override. Unlink overriding an admin controller, here will will put our router info inside the ‘frontend’ tags.
Here is the example for the above controller:
<config> <frontend> <routers> <checkout> <args> <modules> <My_Module before="Mage_Checkout">My_Module_Checkout</My_Module> </modules> </args> </checkout> </routers> </frontend> </config>
Please feel free to ask questions or provide feedback on this post. If there are any errors or better ways to do any of this, please let me know.
Great resource for anyone getting started with Magento, I know that it took me forever find out how to do these and there was never a place that had all of them in one article.
Hi,
I want to override admin Catelog Product Controller for mass Action ..How can I? Can you provide example?
Thanks in Advance
Hiral,
I spelled out the instructions on how to do it pretty clearly in my article. Try it out, play around with it for a while (and make sure the problem isn’t with something other than your overridden controller or config.xml file). If you still can’t get it, post pastebin links of your controller and config.xml file.
Hi,
Is it possible to override the way a specific attribute is presented in the admin?
I have a multi-select attribute with 1K options so I can’t show the admin all of them at once. I want to show a small number of the options and let the admin load the rest with Ajax, similar to the product grid. Is it possible?
Thanks
pablo: This question is not really directly related to this post, but to answer your questions, almost anything is possible. The question is how difficult is it and how long will it take? You may want to reconsider what you are doing with your attributes, as 1k options for 1 attribute is pretty huge, but regardless, I can’t tell you how to do it, but I’m sure there’s a way you could refactor the output of multiselect attributes in the admin. I have never needed to try that, so I can’t tell you if/how possible it is.
Nice and helpful, another good magento blog. thanks!
Thanks a ton, the part on controllers was very helpful.
Unfortunately there is almost always a lot more to overriding a controller. For example you need to ensure that all of the relevant page layout handles are updated to point at the originals and you need to deal with issues like the onepage controller quote coming up blank if you do a naive (but logical) specialisation of the class.
It is these issues that really make the task of rewriting more complex than it should be.
I would like to see a working specialisation of the onepage controller for example showing how the layouts and the quote are set up appropriately.
Whippy – Perhaps you are not overriding the controllers properly then? I haven’t ever encountered the need to change all of the “relevant page layout handles”. The way Magento has set things up is fairly decent. I have overridden many core controllers too.
i tried this, but no luck.
Mycompany_Adminhtml
Jay – I took all these examples from projects that I have done, and even re-tested the article (as I knew it was pretty important to get this one right). There has to be something that you didn’t setup quite right.
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thx for this, very usefull: I keep coming back here
just a small error, I think. In Overriding Core Models, in the rewrite tag you put
My_Module_Block_Sales_Order_Invoice_Itemwhen (i think) it should beMy_Module_Model_Sales_Order_Invoice_Itemie: Model instead of BlockGreat post. I’m trying to do this bit below:
(Code didn’t come through…)
unfortunately… when I use the above in my config.xml, the logout of the system breaks – using 1.4 – did you experience anything like that?
techpop: I do this kind of stuff all the time, and I’ve never had any issues. All of this code was tested on 1.4 without issues.
techpop, I’m having the exact issue using Magento EE 1.9 and I cannot find the solution. I’ve been looking for a while now. Did you ever find a solution?
Thanks,
Justin
Hi!
I have a question about Overriding Admin Core Controllers.
If not specified the name of Controller, as Magento know which class should override?
I like your way to override frontend controllers, thanks!
WebFlakeStudio – Well, as far as I’m concerned, it’s the only proper way to do it
Just a small correction about controllers overloading:
it’s better to use Mage::getModuleDir method for including controllers.
In your sample it will be like this:
require_once Mage::getModuleDir('controllers', ‘Mage_Checkout’) . DS . 'OnepageController.php';
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Thanks for the post. But do you know how do we override a “Base adminhtml controller” in magento. It is different like app\code\core\Mage\Adminhtml\Controller\Action.php i want to override Action.php ?
Hi,
great work, this tutorial is very use full.
Regards,
P.Kannan
Awesome Post, Thank you very much.
Thanks this is so simple after read your post.
I found the best guideline here.
Thanks for give me.
Hey, thanks for this, it is the least painful solution of all out there, especially if you work with more extensions installed.
Thanks! Thanks. I am new to magento and just doing my best to like you guys. Please don’t mind if i ask alot of question in future. I will like to override the customer template, that is, i want that if a customer login into his/her account, they should see a different design. Please help!
keep your good work alive
Best Regards
Max
Hi,
Its not working for me, i want to override newsletter/subscribercontroller.php.
but always default controller run.
config.xml:
CustomCode_MyNewsletter_Mysubscriber
CustomCode_MyNewsletter_Mysubscriber
Hi,
by your tricks can I set $countOfSubscritions = 20 into app/code/core/Mage/Adminhtml/controllers/Newsletter/QueueController.php ?
Thank You and Marry Christmas
Valentino
Very useful blog.
Thanks for share.