class Permission < ActiveRecord::Base
  belongs_to :source, :polymorphic => true
  belongs_to :right, :polymorphic => true

  acts_as_double_polymorphic_join(
    :sources => [:projects, :purchase_orders, :grants],
    :rights => [:languages, :distributions, :media, :editions]
  )
end



class CreatePermissions < ActiveRecord::Migration
  def self.up
    create_table :permissions do |t|
      t.references :source, :polymorphic => true
      t.references :right, :polymorphic => true
      t.timestamps
    end
  end

  def self.down
    drop_table :permissions
  end
end

>> p = Project.find :first
=> #<Project id: 941207533, client_id: 661067193, code: "08-210", title: "California History", series: nil, isbn: "123456789-0", copyright: "2009", number: nil, author: "Sean Schofield", level: "8", imprint: nil, edition: nil, acronym: nil, product_type: 1, created_at: "2008-05-01 09:44:50", updated_at: "2008-05-01 09:44:50">
>> p.languages
=> [#<Language id: 449228226, name: "English + 1", created_at: "2008-05-01 09:44:50", updated_at: "2008-05-01 09:44:50">]
>> p.media
=> [#<Media id: 548512980, name: "Print", created_at: "2008-05-01 09:44:50", updated_at: "2008-05-01 09:44:50">, #<Media id: 349762400, name: "CD-Rom", created_at: "2008-05-01 09:44:50", updated_at: "2008-05-01 09:44:50">]


>> l = Language.find 449228226
=> #<Language id: 449228226, name: "English + 1", created_at: "2008-05-01 09:44:50", updated_at: "2008-05-01 09:44:50">
>> l.projects
=> [#<Project id: 941207533, client_id: 661067193, code: "08-210", title: "California History", series: nil, isbn: "123456789-0", copyright: "2009", number: nil, author: "Sean Schofield", level: "8", imprint: nil, edition: nil, acronym: nil, product_type: 1, created_at: "2008-05-01 09:44:50", updated_at: "2008-05-01 09:44:50">]