path: root/lib/arel/algebra/core_extensions/class.rb

module Arel
  module ClassExtensions
    def attributes(*attrs)
      @attributes = attrs
      attr_reader(*attrs)
    end

    def deriving(*methods)
      methods.each { |m| derive m }
    end

    def derive(method_name)
      methods = {
        :initialize => "
          def #{method_name}(#{@attributes.join(',')})
            #{@attributes.collect { |a| "@#{a} = #{a}" }.join("\n")}
          end
        ",
        :== => "
          def ==(other)
            #{name} === other &&
            #{@attributes.collect { |a| "@#{a} == other.#{a}" }.join(" &&\n")}
          end
        "
      }
      class_eval methods[method_name], __FILE__, __LINE__
    end

    Class.send(:include, self)
  end
end