class User < ActiveRecord::Base
  as_enum :favorites, [:iphone, :ipad, :macbook], accessor: :join_table
end

class AddFavoritesColumnToUser < ActiveRecord::Migration
  def change
    create_join_table :users, :favorites
  end
end

# Migration
add_column :Users, :favorite_cds, :integer
# Model
as_enum :favorites, [:iphone, :ipad, :macbook], accessor: :bitwise

# Model
# serialize :favorite_cds 
# serialize :favorite_cds, YourOwnCoder 
as_enum :favorites, [:iphone, :ipad, :macbook], accessor: :multiple

class User < ActiveRecord::Base
  as_enum :favorites, [:iphone, :ipad, :macbook], accessor: :join_table
end
jane = User.new
jane.favorites = [:iphone, :ipad]
jane.iphone?      # => true
jane.ipad?        # => true
jane.macbook?     # => false
jane.favorites    # => [:iphone, ipad]
jane.favorite_cds # => [0, 1]
joe = User.new
joe.iphone!       # => [:iphone]
joe.favorites     # => [:iphone]
joe.favorite_cds  # => [0]
User.favorites                            # => #<SimpleEnum::Enum:0x0....>
User.favorites[:iphone]                   # => [0]
User.favorites.values_at(:iphone, :ipad)  # => [0, 1]
User.iphones                              # => #<ActiveRecord::Relation:0x0.... [jane, joe]>
# You can also do this since `favorites` returns a 
# #<SimpleEnum::Multiple::CollectionProxy> rather than a #<Array>:
joe = User.new
joe.iphone!       # => [:iphone]
joe.favorites.push :ipad
joe.favorites     # => [:iphone, ipad]
joe.favorite_cds  # => [0, 1]