~michaelforrest/use-case-mapper/trunk

# 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