app/models/permission.rb

	permission.rb revision 0e96fcb3650434da3e94d65e8a6e481253b26cd7
class Permission < ActiveRecord::Base

  ROLES = %w(owner editor)

  # thrown if the last admin/owner tries to remove itself
  class PowerVaccuumError < Exception; end

  attr_accessible :subject, :subject_id, :subject_type, :role

  belongs_to :subject, :polymorphic => true
  belongs_to :item, :polymorphic => true

  validates_inclusion_of :role, :in => ROLES

  scope :item, ->(item) {
    where \
      item_id:   item.id,
      item_type: item.class.to_s
  }

  scope :subject, ->(subject) {
    where \
      subject_id:   subject.id,
      subject_type: subject.class.to_s
  }
end