_nav.html.erb

<%= nav_link 'Button 1', '/salt', :id => 'fun' %>
<%= nav_link 'Button 2', '/pepper' %>
<%= nav_link 'Button 3', '/thyme' %>

helper.rb

def nav_link(link_text, link_path, more_args = nil) 
# link_text: text on the button or link
# link_poth: link url
# more_args: anything you need, like id, alt or title

  class_name = current_page?(link_path) ? 'active' : nil # see if current page is on the link path and apply class 'active', else do nothing
  content_tag(:li, :class => class_name) do
    link_to link_text, link_path, more_args
  end
end