Helper which marks the current page as 'active' in bootstrap navbar

application.html.erb

<div class="navbar navbar-static-top">
  <div class="navbar-inner">
    <div class="container">
      <a class="btn btn-navbar" data-toggle="collapse" data-target=".nav-collapse">
        <span class="icon-bar"></span>
        <span class="icon-bar"></span>
        <span class="icon-bar"></span>
      </a>
      <a class="brand" href="#">Title</a>
      <div class="nav-collapse collapse">
        <ul class="nav pull-right">
          <%= nav_entry 'Home', home_path %>
          <%= nav_entry 'About', about_path  %>
        </ul>
      </div>
    </div>
  </div>
</div>

application_helper.rb

module ApplicationHelper
  def nav_entry(body, path)
    content_tag(:li, link_to(body, path), class: ('active' if current_page?(path)))
  end
end