Navigation helper that adds active class to current page and children

application_helper.rb

module ApplicationHelper

  def nav_link(link_text, link_path, include_children = true)
    if include_children
      class_name = request.fullpath.start_with?(link_path) ? 'active' : ''
    else
      class_name = current_page?(link_path) ? 'active' : ''
    end
    
    content_tag(:li, :class => class_name) do
      link_to link_text, link_path
    end
  end

end