How to sort custom renderer column in magento grid

Question

I want to sort custom rendere column in magento grid.

See below image--

As in above image Sorting is done using Status column, but it is is showing wrong. I want to sort it like active,on hold,out of stock.

Here is the code in Grid.php--

$this->addColumn('stock_status', array(
            'header' => Mage::helper('allstock')->__('Status'),
            'width' => '200px',
            'align' => 'center',
            'index' => 'stock_status',
            'renderer' => 'allstock/adminhtml_allstock_renderer_stockstatus'
        ));

here is the renderer code-

public function render(Varien_Object $row)
    {
        $stock_status=$row->getStockStatus();
        if($stock_status=='stock on hold')
        {
            $html="on hold";
        }
        else
        {
            $html=$stock_status;
        }
        return $html;
    }

Answer 1

Finally I got my answer after working on it a lot, Here is How I made it possible-

/* overwrite to sort stock_status column in grid*/
    protected function _setCollectionOrder($column)
    {
        $collection = $this->getCollection();
        if ($collection) {
             switch ($column->getId()) { 
                  case 'stock_status':
                    $arr = array();
                    $i=0;
                    foreach($collection as $item)  
                    { 
                        if($item->getStockStatus()=="stock on hold")  // check value of column
                        {
                            $item->setStockStatus("on hold");        // replace value of column
                        }   

                        $arr[$i] = $item;   
                        $i++    ;        
                    }

                    $collectionItems = $collection->getItems();
                    usort($collectionItems, array($this, '_sortItems'));  // re-sort collection
                    $newCollection = new Varien_Data_Collection();        // create new collection

                    foreach ($collectionItems as $item) {
                        $newCollection->addItem($item);                // assign each item to new collection
                    }
                    $this->setCollection($newCollection);

                    break;
                default:
                    parent::_setCollectionOrder($column);
                    break;
            }
        }
        return $this;
    }

    /* custom function to sort stock_status column in grid*/
    public function _sortItems($a, $b)
    {
        $columnId = "stock_status";
        $dir      = $this->getParam($this->getVarNameDir(), $this->_defaultDir);

        $al = strtolower($a->getData($columnId));
        $bl = strtolower($b->getData($columnId));

        if ($al == $bl) {
            return 0;
        }

        if ($dir == 'asc') {
            return ($al < $bl) ? -1 : 1;
        } else {
            return ($al > $bl) ? -1 : 1;
        }
    } 

Following links helped me alot--

https://stackoverflow.com/questions/5673093/sort-magento-collection-after-load https://stackoverflow.com/questions/7705007/magento-grid-sorting-on-rendered-column

Answer 2

As it looks that content of your wh1 column is generated in renderer, built-in sorting based on sortable grid config value won't work.

Try to echo you collection select query somewhere in _prepareCollection() method to see how produced SQL query looks:

echo $this->getCollection()->getSelect()

Try to implement sorting in _afterLoadCollection() method after your data is fetched from database. Please find example in answer for following question:

https://stackoverflow.com/questions/7705007/magento-grid-sorting-on-rendered-column

Column isn't Sorting in Custom Admin Report