public function action_index()
{
$category_id = $this->request->param('id');
if (empty($category_id)) {
throw new Exception("Category ID must not be empty!");
}
$topic = new Model_Topic();
$category = new Model_Category();
$view = View::factory('categories/main');
$view->topics = $topic->get_topics_by_id($category_id);
$view->category = $category->get_name($category_id);
$this->template->content = $view->render();
}
