class Edition < ActiveRecord::Base  has_and_belongs_to_many :works  has_many   :orders  belongs_to :publisher  def Edition.of_works(works)    works.map {|work| work.editions }.flatten.uniq  end  def composers    works.map {|work| work.composer }.uniq  end# The edition might have a title of its own.  If not,# fall back on the title of the first (and perhaps only)# work in the edition.  def nice_title    (title || works[0].nice_title) +     " (#{publisher.name}, #{year})"  endend