1

➜ cat test_cattr_accessor.rb 
require 'rubygems'
require 'active_support/all'

class A
  cattr_accessor :attribute
end

class B
  cattr_accessor :attribute
end

A.attribute = "PASS"
B.attribute = "FAIL"
puts A.attribute
➜ rvm use system
Now using system ruby.
➜ ruby test_cattr_accessor.rb 
PASS
➜ ~/tmp/rubinius/bin/rbx -v
rubinius 1.2.1dev (1.8.7 a0ef1c8f 2010-12-21 JI) [x86_64-apple-darwin10.6.0]
➜ ~/tmp/rubinius/bin/rbx test_cattr_accessor.rb
FAIL
➜ rvm use rbx-1.2.0
Using /Users/mutle/.rvm/gems/rbx-1.2.0-20101221
➜ ruby test_cattr_accessor.rb
FAIL
➜ rvm use rbx-1.1.1
Using /Users/mutle/.rvm/gems/rbx-1.1.1-20101116
➜ ruby test_cattr_accessor.rb
FAIL
➜ rvm use rbx-1.1.0
Using /Users/mutle/.rvm/gems/rbx-1.1.0-20100923
➜ ruby test_cattr_accessor.rb                  
PASS
➜ rvm use rbx-1.0.1 
Using /Users/mutle/.rvm/gems/rbx-1.0.1-20100603
➜ ruby test_cattr_accessor.rb
PASS

2

require 'rubygems'

module ClassAttribute
  class << self
    def included(mod)
      mod.class_eval <<-EOS
        unless defined? @@attribute
          @@attribute = nil
        end
        def self.attribute
          @@attribute
        end
        def self.attribute=(obj)
          @@attribute = obj
        end
      EOS
    end
  end
end

class A
  include ClassAttribute
  # --- This code works ---
  # unless defined? @@attribute
  #   @@attribute = nil
  # end
  # def self.attribute
  #   @@attribute
  # end
  # def self.attribute=(obj)
  #   @@attribute = obj
  # end
end

class B
  include ClassAttribute
  # --- This code works ---
  # unless defined? @@attribute
  #   @@attribute = nil
  # end
  # def self.attribute
  #   @@attribute
  # end
  # def self.attribute=(obj)
  #   @@attribute = obj
  # end
end

A.attribute = "PASS"
B.attribute = "FAIL"
puts A.attribute

# - FAIL in rbx, PASS in 1.8.7