a.rb

# config/initializers/trailing_slash.rb


Rails.configuration.before_initialize do

  ActionController::Base.module_eval do
    before_filter :enforce_trailing_slash

  protected
    def enforce_trailing_slash
      ext = request.fullpath.split('.', 2)[1]

      if ext.nil? and request.format.to_s == 'text/html'
        url = request.original_url

        if request.get? && !url.ends_with?('/')
          redirect_to(url + '/')
          return
        end
      end
    end
  end

end