memoize.rb

1.9.3-p448 :014 > class MyClass
1.9.3-p448 :015?>   def my_config
1.9.3-p448 :016?>     @@my_config ||= nil
1.9.3-p448 :017?>     end
1.9.3-p448 :018?>   def my_config=(setting)
1.9.3-p448 :019?>     @@my_config = setting
1.9.3-p448 :020?>     end
1.9.3-p448 :021?>   end
1.9.3-p448 :022 > config = MyClass.new
 => #<MyClass:0x007faa21080d40>
1.9.3-p448 :023 > config.my_config
 => nil
1.9.3-p448 :024 > config.my_config = false
 => false
1.9.3-p448 :025 > config.my_config
 => nil
1.9.3-p448 :026 > config.my_config = true
 => true
1.9.3-p448 :027 > config.my_config
 => true
 1.9.3-p448 :028 > class MyClass
1.9.3-p448 :029?>   def my_config
1.9.3-p448 :030?>     defined?(@@my_config) ? @@my_config : nil
1.9.3-p448 :031?>     end
1.9.3-p448 :032?>   end
1.9.3-p448 :035 > MyClass.remove_class_variable(:@@my_config)
 => true
1.9.3-p448 :036 > config.my_config
 => nil
1.9.3-p448 :037 > config.my_config = false
 => false
1.9.3-p448 :038 > config.my_config
 => false