<=> (DataMapper::Resource)

    # File lib/dm-core/resource.rb, line 435
        def <=>(other)
          unless other.kind_of?(model.base_model)
            raise ArgumentError, "Cannot compare a #{other.model} instance with a #{model} instance"
          end
          cmp = 0
          model.default_order(repository_name).each do |direction|
            cmp = direction.get(self) <=> direction.get(other)
            break if cmp != 0
          end
          cmp
        end