## body_helper.rb
module BodyHelper


  def body_class(body_class)
    @body_class ||= ""
    @body_class << "#{body_class}"
  end

end

## application_controller.rb

class ApplicationController < ActionController::Base
  protect_from_forgery

  helper :all

  before_filter :setup_menu
  def setup_menu
    #look into building a hash
    #@nav_data[:authors] = Author.all
    @all_authors = Author.order(:name)
    @genres = Genre.all
  end
end

##books_controller.rb

  def index
    @books = Book.order(:title)
    body_class "books"
  end