gistfile1.rb

class C
  @v = "Bah bah"

  def m
    p @v
    p @@v # The Class instance variable is not the same as a class variable
  end

  def self.m
    p @v
  end


end


# Create c = C.new
# c.m
# NameError: uninitialized class variable @@v in C
#  from /Users/user/Development/ruby/wgr/scope.rb:5:in `m'
#  from (irb):4
#	 from /Users/user/.rbenv/versions/1.9.3-p327/bin/irb:12:in `<main>'