ruby object model class variables

class_variables.rb

@@test = 20

class A
  @@a = 1
  def self.a
    @@a
  end

  def hello
    puts "hello from A"
  end
end

class B < A
  @@a = 22

  def hello
    puts "hello from B"
  end
end

puts @@test

a = A.new
a.hello
puts A.a

b = B.new
b.hello
puts B.a

~ > ruby test.rb
20
hello from A
22
hello from B
22