Default vars for parser->parse

[eluser]woutr_be[/eluser]
I'm fairly new to CodeIgniter, but I'm just learning by doing.

I've overwritten the default CI_Controller in order to load views in my general template, like this:

Code:

class Guest_Controller extends CI_Controller
{  
private $body_classes = "guest ";

public function __construct()
{
  parent::__construct();
}

public function _output($content)
{
  // Load the base template with output content available as $content
  $data['content'] = &$content;  
  echo($this->load->view('templates/html_guest', $data, true));
}
}

I also want to use this to do some extra authentication checks, like some user are only allowed certain controllers.

Now when I use this Guest_Controller, like this:

Code:

class Homepage extends Guest_Controller {

public function __contruct()
{
}

public function index()
{
  $data = array(
   'title' => 'Homagepage',
   'page_title' => 'Test title',
   'body_classes' => 'guest home'
  );
  $this->parser->parse('homepage', $data);
}
}

I now want to add some default string to my "body_class", the one that is defined in my Guest_Controller.
Is there a way to override parser->parse in my Guest_Controller in orde to do so?

This doesn't have to be parser->parse, but I can also just use $this->load->view if it's easier that way.