Cannot access type method on Ruby class

The following code is copied from the site - http://www.w3cschool.cc/ruby/ruby-object-oriented.html. Note, it is at the bottom.  However, I got one error message during runing it.

#!/usr/bin/ruby -w
class Box
  # 输出类信息
  puts "Type of self = #{self.type}"
  puts "Name of self = #{self.name}"
end

The output error message:

D:\Ruby\bin\ruby.exe -e $stdout.sync=true;$stderr.sync=true;load($0=ARGV.shift) D:/Ruby/RubyStudyPro/box.rb
D:/Ruby/RubyStudyPro/box.rb:4:in `<class:Box>': undefined method `type' for Box:Class (NoMethodError)
 from D:/Ruby/RubyStudyPro/box.rb:2:in `<top (required)>'
 from -e:1:in `load'
 from -e:1:in `<main>'

Process finished with exit code 1

Who could kindly give me some tips?