class Person attr_reader :name, :age def initialize(name, age) @name, @age = name, age end def to_str @name end end class NotStringPerson attr_reader :name, :age def initialize(name, age) @name, @age = name, age end def to_s @name end end tanaka = Person.new("tanaka", 34) suzuki = NotStringPerson.new("suzuki", 44) puts "■ to_s, to_str を直接呼び出し" puts "tanaka.to_s = " + tanaka.to_s puts "tanaka.to_st