ActiveSupport::Concern と、Module#concerning ref: http://qiita.com/kasei-san/items/c016c626836da09a5a70

file0.txt

関心事、関連、利害関係 など

file3.txt

irb(main):001:0> m = Member.new
=> #<Member:0x007f92cfae15c8>
irb(main):002:0> m.name = "二郎"
=> "二郎"
irb(main):003:0> m.default_name?
=> false
irb(main):004:0> m.name = "太郎"
=> "太郎"
irb(main):005:0> m.default_name?
=> true

human.rb

module Human
  extend ActiveSupport::Concern

  included do
    attr_accessor :name
    def self.default_name
      "太郎"
    end

    def default_name?
      name == self.class.default_name
    end
  end
end

member.rb

class Member
  include Human
end

class Member
  concerning :Human do
    included do
      attr_accessor :name
      def self.default_name
        "太郎"
      end

      def default_name?
        name == self.class.default_name
      end
    end
  end
end