Class#inherited

>> class Class
>>   def inherited(subclass)
>>      puts "#{self}'s subclass:#{subclass} is defined"
>>       subclass.instance_variable_set('@klass_hensu', "KlassHensu")
>>   end
>> end
=> nil


>> class Hoge
>>   def self.hoge
>>     @klass_hensu
>>   end
>> end
=> nil
>> Hoge.hoge
=> "KlassHensu"

クラスのインスタンス変数・・