making attr_* method by Ruby code

attr_dsl.rb

#内部DSLのソースコード                                                          
class Module
  def attr_reader(*symbols)
    symbols.each do |symbol|
      class_eval %(
        def #{symbol}
          @#{symbol}
        end
      )
    end
  end

  def attr_writer(*symbols)
    symbols.each do |symbol|
      class_eval %{
        def #{symbol}= (value)
          @#{symbol} = value
        end
      }
    end
  end

  def attr_accessor(*symbols)
    attr_reader(*symbols)
    attr_writer(*symbols)
  end
end

class A
  attr_accessor :id, :color
end

a = A.new
a.id = 1
p a.id

class B
  def foo(*s)
    p s
  end
end
foo = B.new.foo(1, :id)
# https://www.xmisao.com/2014/02/10/ruby-attr-accessor-attr-reader-attr-writer.h
tml
# http://gihyo.jp/admin/feature/01/dsl/0001?page=2