ruby_class_varible2.rb

@@ha = 'ha'
class A
  @ha = 'boom'
  class << self
    attr_accessor :ha
  end

  def self.my_method
    "k" + self.ha
  end
end

p @@ha
# "ha"
p A.ha
# "boom"
p A.my_method
# "kboom"