gistfile1.rb

class ObjectBuilder
  def prototype(proto)
    # Leave method implementations on the proto object
    ivars = proto.instance_variables.reject{ |ivar_name|
      proto.respond_to?(ivar_name.to_s[1..-1]) &&
      proto.instance_variable_get(ivar_name).is_a?(Proc)
    }
    ivars.each do |ivar_name|
      unless @object.instance_variable_defined?(ivar_name)
        @object.instance_variable_set(
          ivar_name,
          proto.instance_variable_get(ivar_name).dup)
      end
    end
    @object.extend(Prototype.new(proto))
  end
end