vendor/rails/activesupport/lib/active_support/core_ext/class/delegating_attributes.rb

   1 # These class attributes behave something like the class
   2 # inheritable accessors.  But instead of copying the hash over at
   3 # the time the subclass is first defined,  the accessors simply
   4 # delegate to their superclass unless they have been given a
   5 # specific value.  This stops the strange situation where values
   6 # set after class definition don't get applied to subclasses.
   7 class Class
   8   def superclass_delegating_reader(*names)
   9     class_name_to_stop_searching_on = self.superclass.name.blank? ? "Object" : self.superclass.name
  10     names.each do |name|
  11       class_eval <<-EOS
  12       def self.#{name}
  13         if defined?(@#{name})
  14           @#{name}
  15         elsif superclass < #{class_name_to_stop_searching_on} && superclass.respond_to?(:#{name})
  16           superclass.#{name}
  17         end
  18       end
  19       def #{name}
  20         self.class.#{name}
  21       end
  22       def self.#{name}?
  23         !!#{name}
  24       end
  25       def #{name}?
  26         !!#{name}
  27       end
  28       EOS
  29     end
  30   end
  31
  32   def superclass_delegating_writer(*names)
  33     names.each do |name|
  34       class_eval <<-EOS
  35         def self.#{name}=(value)
  36           @#{name} = value
  37         end
  38       EOS
  39     end
  40   end
  41
  42   def superclass_delegating_accessor(*names)
  43     superclass_delegating_reader(*names)
  44     superclass_delegating_writer(*names)
  45   end
  46 end