adding custom fields to cart rules's general information tab

Question

i want to add a custom fields in cart rules's general information tab, the data will be stored in additional table with corresponding cart rules id.

what is the best practice to do this? should i use rewrite to do this? so rewrite which class? and what observer should be used?

Answer 1

To me you should definitely use observers.

I'm not gonna go through the process of creating an additional database table. Just don't forget to create the related model/resource models/collection classes for your new entity.

Then you can observe the following adminhtml events:

• adminhtml_promo_quote_edit_tab_main_prepare_form: this one is called during the shopping cart rule form preparation and will be used to add your new field
• controller_action_postdispatch_adminhtml_promo_quote_save: this one is called after you saved the shopping cart rule.

Example:

<adminhtml>
    <events>
        <!-- Called during the form preparation -->
        <adminhtml_promo_quote_edit_tab_main_prepare_form>
            <observers>
                <custom_prepare_quote_form>
                    <type>singleton</type>
                    <class>module/admin_observer</class>
                    <method>prepareQuoteForm</method>
                </custom_prepare_quote_form>
            </observers>
        </adminhtml_promo_quote_edit_tab_main_prepare_form>
        <!-- Called once the save customer group action has been called -->
        <controller_action_postdispatch_adminhtml_promo_quote_save>
            <observers>
                <custom_promo_quote_save>
                    <type>singleton</type>
                    <class>module/admin_observer</class>
                    <method>promoQuoteSave</method>
                </custom_promo_quote_save>
            </observers>
        </controller_action_postdispatch_adminhtml_promo_quote_save>
    </events>
</adminhtml>

Then in your Admin/Observer.php you can do the following:

public function prepareQuoteForm(Varien_Event_Observer $observer)
{
    // Get form
    /** @var Mage_Adminhtml_Block_Promo_Quote_Edit_Tab_Main $form */
    $form = $observer->getEvent()->getForm();
    // Get fieldset
    $fieldset = $form->getElement('base_fieldset');
    // Add the field
    $fieldset->addField('my_custom_field', 'text',
        [
            'name'      => 'my_custom_field',
            'label'     => Mage::helper('module')->__('My Custom Field'),
            'title'     => Mage::helper('module')->__('My Custom Field'),
            'required'  => false
        ]
    );
}

This method will add your field to the form. After that code I suggest you load your custom entity corresponding to the shopping cart rule and use $form->addValues() to add the values to the form so it reflects data from the DB

The second method:

public function promoQuoteSave(Varien_Event_Observer $observer)
{
    // Get the action
    $action = $observer->getEvent()->getControllerAction();
    // Get the data
    $data = $action->getRequest()->getParams();
    // Add your custom entity data to the DB
}

This method needs to be used to add your custom data to your additional DB table so you'll have to write that code.