+# These class attributes behave something like the class
+# inheritable accessors. But instead of copying the hash over at
+# the time the subclass is first defined, the accessors simply
+# delegate to their superclass unless they have been given a
+# specific value. This stops the strange situation where values
+# set after class definition don't get applied to subclasses.
+class Class
+ def superclass_delegating_reader(*names)
+ class_name_to_stop_searching_on = self.superclass.name.blank? ? "Object" : self.superclass.name
+ names.each do |name|
+ class_eval <<-EOS
+ def self.#{name} # def self.only_reader
+ if defined?(@#{name}) # if defined?(@only_reader)
+ @#{name} # @only_reader
+ elsif superclass < #{class_name_to_stop_searching_on} && # elsif superclass < Object &&
+ superclass.respond_to?(:#{name}) # superclass.respond_to?(:only_reader)
+ superclass.#{name} # superclass.only_reader
+ end # end
+ end # end
+ def #{name} # def only_reader
+ self.class.#{name} # self.class.only_reader
+ end # end
+ def self.#{name}? # def self.only_reader?
+ !!#{name} # !!only_reader
+ end # end
+ def #{name}? # def only_reader?
+ !!#{name} # !!only_reader
+ end # end
+ EOS
+ end
+ end
+
+ def superclass_delegating_writer(*names)
+ names.each do |name|
+ class_eval <<-EOS
+ def self.#{name}=(value) # def self.only_writer=(value)
+ @#{name} = value # @only_writer = value
+ end # end
+ EOS
+ end
+ end
+
+ def superclass_delegating_accessor(*names)
+ superclass_delegating_reader(*names)
+ superclass_delegating_writer(*names)
+ end
+end