Adding custom column into product grid

Question

I have created a custom column for associated products (basically every simple product will have that column under "associated products" tab of configurable product). I store information of this field/column into an attribute which belong to configurable product instead of each simple product.

Below is the code for adding a column;

config.xml

<core_block_abstract_to_html_before>
 <observers>
 <something>
 <class>namespace_JsonProductInfo_Model_Observer</class>
 <method>addPositionColumn</method>
 </something>
 </observers>
</core_block_abstract_to_html_before>

Oberver.php

public function addPositionColumn(Varien_Event_Observer $observer)
{
 $block = $observer->getEvent()->getBlock();
 if ($block instanceof Mage_Adminhtml_Block_Catalog_Product_Edit_Tab_Super_Config_Grid) {
 if (!$block->isReadonly()) {
 $block->addColumnAfter(
 'position_simple',
 array(
 'header' => Mage::helper('jsonproductinfo')->__('Position'),
 'type' => 'input',
 'name' => 'position_simple',
 'index' => 'position_simple',
 'sortable' => false,
 ),
 'name'
 );
 }
 }
}

With above code I am able to add the column into a require grid. And I am also able to save the information which I put inside that column (which is basically an attribute). The only problem I am facing is, I am unable to display the stored information into that column again (If I edit the product). I have also created another observer of type eav_collection_abstract_load_befor but no luck so far. Below is the code for it:

config.xml

<eav_collection_abstract_load_before>
 <observers>
 <jsonproductinfo>
 <class>namespace_JsonProductInfo_Model_Observer</class>
 <method>addPositionToCatalogProductCollection</method>
 </jsonproductinfo>
 </observers>
</eav_collection_abstract_load_before>

Observer.php

public function addPositionToCatalogProductCollection($observer)
{
 $collection = $observer->getEvent()->getCollection();
 if (!isset($collection)) {
 return;
 }
 $collection->addAttributeToSelect('position_simple');
}

I would be grateful if someone can point to the mistake or guide me how can I display back that information again into that column.

---

EDIT

And here is the code which creates the "postion_simple".

$this->addAttribute(
 'catalog_product',
 'position_simple',
 array(
 'group' => 'General',
 'type' => 'varchar',
 'input' => 'hidden',
 'backend' => '',
 'frontend' => '',
 'label' => 'Simple Position',
 'class' => '',
 'source' => '',
 'global' => Mage_Catalog_Model_Resource_Eav_Attribute::SCOPE_GLOBAL,
 'visible' => true,
 'required' => false,
 'user_defined' => true,
 'default' => '',
 'searchable' => false,
 'filterable' => false,
 'comparable' => false,
 'visible_on_front' => false,
 'visible_in_advanced_search' => false,
 'unique' => false,
 'apply_to' => Mage_Catalog_Model_Product_Type::TYPE_CONFIGURABLE,
 'is_configurable' => false,
 )
);

• Minesh Patel: have you checked that your observer is working ? check by printing query in your observer.echo $collection->getSelect()
• Capri82: @MineshPatel, Yes, the observer is working. I was already sure about it but still checked it by printing the query.

Answer 1

1. change 'index' => 'position_simple' to 'index' => 'entity_id' in your Observer.php (function addPositionColumn)
2. you need to get value of your position_simple attribute from configurable product and use it in added column - one way to do that:

create function in Observer.php

protected function _getDefaultConfigurationId() {
 /** @var Mage_Catalog_Model_Product $product */
 $product = Mage::registry('current_product');
 if ($product) {
 return array($product->getData('position_simple'));
 }
 return '';
}

and use that in your addPositionColumn function like that:

... 
'values' => $this->_getDefaultConfigurationId(),
...

After that, there is no need of observer type eav_collection_abstract_load_befor at all.