class User
  include DataMapper::Resource


  property :id,               Serial
  property :priority,         Integer
end

class Posting
  property :id,               Serial
  property :user_id,          Integer, :index => true
  belongs_to :user
end

# This used to work but I get this error: +options[:order]+ entry :priority does not map to a property in Posting
Posting.all(:order => [DataMapper::Query::Direction.new(User.properties[:priority], :desc)], :links => [:user])