gistfile1.rb

  def find_readable(*args)
    type = args[0].to_s.capitalize
    args.shift
    cond = priv_conditions(type, :read => true)
    type.constantize.find(*args).where(*cond)
  end

  private
  def priv_conditions(type, rw)
    # Pure ruby way
    #privileges.find_all_by_target_type_and_read(type.to_s.capitalize, true, :include => :target).map { |p| p.target}
    ["id in (select target_id from privileges where group_id = ? and target_type = ? #{'and read = ?' if rw.has_key?(:read)}  #{'and write = ?' if rw.has_key?(:write)})", id, type, rw[:read], rw[:write]]
  end