protected function renderCells()
    {
        $row = $this->getDataRow();
        $out = '';
        foreach($this->grid->getConfig()->getColumns() as $column) {
            $component = new TableCell($column);
            $component->initialize($this->grid);
            $component->setContent($column->getValue($row));
            $out .= $component->render();
        }
        return $out;
    }