Overwrite and call collection

Question

I want to extend Mage_Sales_Model_Resource_Order_Shipment_Item_Collection because it doesn't come with a getIntervals() function.

So I created following files:

MyModule/Modulename/Model/Mysql4/Shipping/Collection:

class MyModule_Modulename_Model_Mysql4_Shipping_Collection 
extends Mage_Core_Model_Mysql4_Collection_Abstract {

public function _construct() {
    parent::_construct();
    $this->_init('sales/order_shipment_item_collection');
}

MyModule/Modulename/etc/config.xml

<global>
    <models>
        <modulename>
            <class>MyModule_Modulename_Model</class>
            <resourceModel>modulename_mysql4</resourceModel>
        </modulename>
        <modulename_mysql4>
            <class>MyModule_Modulename_Model_Mysql4</class>
        </modulename_mysql4>
    </models>
</global>

In my order grid I want to call the collection with

$collection = Mage::getResourceModel('modulename/mymodule_modulename_shipping_collection');

But the collection is empty and I can't figure out why. Can anyone point me in the right direction, please?

Answer 1

I want to extend Mage_Sales_Model_Resource_Order_Shipment_Item_Collection

But you didn't. You extended Mage_Core_Model_Mysql4_Collection_Abstract. The _init() parameter is used to determine the model which belongs to the collection, you cannot use it to extend another collection.

So change the class to

class MyModule_Modulename_Model_Mysql4_Shipping_Collection extends Mage_Sales_Model_Resource_Order_Shipment_Item_Collection
{
    // add your getInterval() method here
}