gistfile1.rb

def active_class(controller, action = nil)
    active = params[:controller] == controller.to_s &&
              (action.nil? || params[:action] == action.to_s) 

    active ? "active" : nil
end

def nav_link(link_text, controller)
    content_tag(:li, :class => active_class(controller, action) do
	    link_to link_text, controller
    end
end