dynamic select models

gistfile1.rb

# app/models/artist.rb
class Artist < ActiveRecord::Base
  belongs_to :genre

  has_many :songs

  attr_accessible :genre_id, :name, :genre
end

# app/models/genre.rb
class Genre < ActiveRecord::Base
  attr_accessible :name

  has_many :artists
  has_many :songs, :through => :artists
end

# app/models/songs.rb
class Song < ActiveRecord::Base
  belongs_to :artist

  attr_accessible :artist_id, :title, :artist
end