Best Practice: How to add a column to a backend grid ?

Question

Usually we need to add to the Order Grid some column, so let take this as example.

There are 3 ways to do that:

1. Rewrite the grid block in our custom module
2. Use an observer on the event core_block_abstract_prepare_layout_before
3. Use a Layout update

(let don't consider the alteration of the collection to make things more easy)

• First method is the most powerful but It leads to conflict in the scenarios.
• Second method is in IMHO resource consuming as we are adding an extra code step for every block we are going to render
• Third step is a layout update so should be the most advisable ... but are we sure it will work always ?

Other consideration are welcome

References:
Method 1: - http://inchoo.net/ecommerce/magento/programming-magento/adding-customer-group-column-to-sales-grid-in-magento/
Method 2: - http://www.atwix.com/magento/add-column-to-customers-grid-alternative-way/
Method 3: - http://www.atwix.com/magento/column-to-orders-grid/

Answer 1

Best practice to add a column to the backend grid is of course implementation of event-observer method. But question arises which event is used for the purpose? And one of the Answer is core_block_abstract_to_html_before

Suppose say you have implemented observer model for above event with method coreBlockAbstractToHtmlBefore.

CODE:

public function coreBlockAbstractToHtmlBefore(Varien_Event_Observer $observer)
{

    /** @var $block Mage_Core_Block_Abstract */
    $block = $observer->getEvent()->getBlock();
    if ($block->getId() == 'customerGrid')
    {
        // Add the attribute as a column to the grid
        $block->addColumnAfter(
            'custom_grid_element',
            array(
                'header' => $helper->__('Custom Grid Element'),
                'align' => 'center',
                'width' => '80px',
                'type' => 'text',
                'options' => array(
                ),
                'default' => '',
                'index' => 'custom_grid_element',
                'renderer'  => ''
            ),
            'customer_since'
        );

        // Set the new columns order.. otherwise our column would be the last one
        $block->sortColumnsByOrder();
    }
}

Above is just an example for adding custom grid element to the Customer grid. You can deploy the very same technique for Sales grid as well.

Answer 2

If you want to use on observer try adminhtml_block_html_before instead of core_block_abstract_to_html_before

You could also use your module adminhtml layout.xml

    <?xml version="1.0"?>
    <layout>
    <add_order_grid_column_handle>
        <reference name="sales_order.grid">
            <action method="addColumnAfter">
                <columnId>magepal_internal_order_num</columnId>
                <arguments module="sales" translate="header">
                    <header>MagePal #</header>
                    <index>magepal_internal_order_num</index>
                    <type>text</type>
                    <width>110px</width>
                </arguments>
                <after>shipping_name</after>
            </action>
        </reference>
    </add_order_grid_column_handle>
    <adminhtml_sales_order_grid>
        <update handle="add_order_grid_column_handle" />
    </adminhtml_sales_order_grid>
    <adminhtml_sales_order_index>
        <update handle="add_order_grid_column_handle" />
    </adminhtml_sales_order_index>
    <layout>

See Add new field to administration orders grid

Answer 3

The best way to add a column to the order grid is to create an observer for the sales_order_resource_init_virtual_grid_columns event. Just add a column to the sales_flat_order_grid table in your install script and use this event to store the data directly into the table at every order save. This way there is no need for any joins when showing the grid to the user. For more details on how to setup the column see http://www.ecomdev.org/2010/07/27/adding-order-attribute-to-orders-grid-in-magento-1-4-1.html