How to override _prepareCollection and _prepareColumns in Magento Admin - magento

Question

How to override _prepareCollection and _prepareColumn from core to local. I want to add new column in a grid. How to do this?
protected function _prepareCollection()
{
$collection = Mage::getModel('players/players')->getCollection();
$this->setCollection($collection);
return parent::_prepareCollection();
}
protected function _prepareColumns()
{
$this->addColumn('player_id', array(
'header' => Mage::helper('players')->__('ID'),
'align' =>'right',
'width' => '50px',
'index' => 'player_id',
));
$this->addColumn('name', array(
'header' => Mage::helper('players')->__('Name'),
'align' =>'left',
'index' => 'name',
));
return parent::_prepareColumns();
}

Answer 1

Well there are two ways to do it. The first, while easier is not preferred, is to "local include hack" it and move the grid from core/Mage/../.. to local/Mage../.. and simply make your changes are required.
The alternative is to do a rewrite of the file in a module config.xml:
<blocks>
<customadminhtml>
<class>Namespace_CustomAdminhtml_Block</class>
</customadminhtml>
<adminhtml>
<rewrite>
<sales_order_grid>Namespace_CustomAdminhtml_Block_Adminhtml_Sales_Order_Grid</sales_order_grid>
</rewrite>
</adminhtml>
</blocks>
In the rewritten file I would not both trying to override the "_prepareCollection" call. How are you going to call it and set the collection, logically, you can't insert your changes in there properly and still maintain original functionality. Instead I would override the "setCollection" method. By doing this you maintain the logic of the original _prepareCollection function and can insert your logic into the flow:
/**
* #brief Add customer_email to sales order
* #param Mage_Sales_Model_Resource_order_grid_collection $collection
*/
public function setCollection($collection)
{
/** #var Mage_Eav_Model_Config $eav */
$eav = Mage::getModel('eav/config');
$attribute = $eav->getAttribute('customer', 'customer_number');
$connection = $collection->getConnection();
$collection->join(array('sfo' => 'sales/order'), 'main_table.entity_id=sfo.entity_id', 'customer_email');
if ($attribute->getId()) {
$collection->getSelect()
->joinLeft(array('c' => $connection->getTableName('customer_entity_varchar')),
'main_table.customer_id = c.entity_id AND c.attribute_id = '.$attribute->getId(),
array('customer_number' => 'value'));
}
parent::setCollection($collection);
}
Finally, you can add the column by overriding the normal "_prepareColumns" function, just call the parent before hand:
public function _prepareColumns()
{
parent::_prepareColumns();
$this->addColumnAfter('customer_email', array(
'header' => Mage::helper('customer')->__('Customer Email'),
'width' => '50px',
'index' => 'customer_email',
), 'shipping_name');
$this->sortColumnsByOrder();
return $this;
}