how to prerender/preprocess the data before displaying in custom admin module grid?

Question

i have a custom admin module will print some data

$this->addColumn('product_old_values', array(
    'header'    => Mage::helper('adminlog')->__('product_old_values'),
    'align'     =>'left',
    'width'     => '20%',
    'index'     => 'product_old_values',
)); 

since product_old_values is a serialized array (a long string), how can i run unserialize(product_old_values) before displaying into a grid?

Answer 1

render the column by below code

$this->addColumn('product_old_values', array(
    'header'    => Mage::helper('adminlog')->__('product_old_values'),
    'align'     =>'left',
    'renderer'  => 'Namespace_Modulename_Block_Adminhtml_Gridrender',
    'width'     => '20%',
    'index'     => 'product_old_values',
)); 

FOR RENDERING

class Namespace_Modulename_Block_Adminhtml_Gridrender extends Mage_Adminhtml_Block_Widget_Grid_Column_Renderer_Abstract
    {

        public function render(Varien_Object $row)
        {
         }
    }

for doing in grid class

 $this->addColumn('product_old_values', array(
        'header'    => Mage::helper('adminlog')->__('product_old_values'),
        'align'     =>'left',            
        'width'     => '20%',
        'index'     => 'product_old_values',
       'frame_callback' => array($this, 'callback_image')

    ));



public function callback_image($value)
 {
   //write your code
 }