SKU custom column on sales order grid causing non-static issue

Question

I have followed the guide here by Volodymyr Vygovskyi, everything is working well, apart from when you filter by a sku, it causes the issue:

Strict Notice: call_user_func() expects parameter 1 to be a valid callback, non-static method Atwix_ExtendedGrid_Model_Observer::filterSkus() should not be called statically in /Applications/XAMPP/xamppfiles/htdocs/mag19/app/code/core/Mage/Adminhtml/Block/Widget/Grid.php on line 468

Investigating this I can see that he has the following as his filter_condition_callback:

'filter_condition_callback' => array('Atwix_ExtendedGrid_Model_Observer', 'filterSkus'),

whereby the observer is being called statically here:

'Atwix_ExtendedGrid_Model_Observer'

In my attempts to fix this, I changed this to the variable $this, which causes the filterSkus function to not be found.

Thus, I then attempted to move the filter function to the helper data.php file. This then led to the sku column in sales_flat_order_item to not be found.

Likewise also tried changing the string declaration of the observer to Mage::getSingleton('Atwix_ExtendedGrid_model_observer'). But, this then causes the following error:

SQLSTATE[42S22]: Column not found: 1054 Unknown column 'sales_flat_order_item.sku' in 'where clause', query was: SELECT COUNT(DISTINCT main_table.entity_id) FROM `sales_flat_order_grid` AS `main_table` WHERE ((sales_flat_order_item.sku like '%lab%'))

I am at a loggerhead with how to fix this issue, thus was hoping someone could help me.

Answer 1

I have managed to solve this via the following:

1. changing the string declaration of the observer to Mage::getSingleton('Atwix_ExtendedGrid_model_observer')

2. Added the following missing join to the salesOrderGridCollectionLoadBefore function:

   $select->join('sales_flat_order_item', 'sales_flat_order_item.order_id=main_table.entity_id', array('skus' => new Zend_Db_Expr('group_concat(sales_flat_order_item.sku SEPARATOR ", ")')));