理解不能

atmark_variables.rb

class Foo
  @baz = 1
  @@bar = 2
  def self.baz; @baz; end
  def self.baz=(n); @baz=n; end
  def self.bar; @@bar; end
  def self.bar=(n); @@bar=n; end
end

class Hoge < Foo
end

p Foo.baz # => 1
p Foo.bar # => 2
p Hoge.baz # => nil
p Hoge.bar # => 2

__foo__ = Foo.clone

Foo.baz = 2
Foo.bar = 1

p __foo__.baz # => 1
p __foo__.bar # => 1