magento Adminhtml Users Grid by Role Id add column

Question

I can filter the adminhtml users grid to only show users with a specific role ID as code in

\app\code\local\Mage\Adminhtml\Block\Permissions\User\grid.php

=> for collection

 protected function _prepareCollection()
{

    $collection = Mage::getResourceModel('admin/user_collection');
    $collection->getSelect()->join(array('ar' =>'admin_role'),'ar.user_id = admin_user.user_id')
    ->reset('columns')->columns(array('role_id'));
    $this->setCollection($collection);
    return parent::_prepareCollection();

}

=>and for add column

 protected function _prepareColumns()
{
  parent::_prepareColumns(); 
    $this->addColumn('role_id', array(
        'header'    =>Mage::helper('adminhtml')->__('Role ID'),
        'index'     =>'role_id',
        'align'     => 'right',
        'width'    => '50px'
    ));

But still not getting roll id in column ..

Answer 1

Replace following code.

$collection->getSelect()->join(
            array('ar' =>'admin_role'),
            'ar.user_id = main_table.user_id',
            array('role_id')
        );

So _prepareCollection looks like:

protected function _prepareCollection()
    {
        $collection = Mage::getResourceModel('admin/user_collection');
        $collection->getSelect()->join(
            array('ar' =>'admin_role'),
            'ar.user_id = main_table.user_id',
            array('role_id')
        );
        $this->setCollection($collection);
        return parent::_prepareCollection();
    }