From: dreamcat four <dreamcat4@...>
Date: 2009-10-11T03:02:32+09:00
Subject: Class Level inheritable attributes - are we there yet?

Hi,
I'm having trouble understanding why this isn't available from the Ruby core?
Does core not provide an alternative / satisfactory implementation of this?

# clia.rb - Class Level Inheritable Attributes

module ClassLevelInheritableAttributes
  def self.included(base)
    base.extend(ClassMethods)
  end

  module ClassMethods
    def inheritable_attributes(*args)
      @inheritable_attributes ||= [:inheritable_attributes]
      @inheritable_attributes += args
      args.each do |arg|
        class_eval %(
          class << self; attr_accessor :#{arg} end
        )
      end
      @inheritable_attributes
    end

    def inherited(subclass)
      @inheritable_attributes.each do |inheritable_attribute|
        instance_var = "@#{inheritable_attribute}"
        subclass.instance_variable_set(instance_var,
instance_variable_get(instance_var))
      end
    end
  end
end

class Polygon
  include ClassLevelInheritableAttributes
  inheritable_attributes :sides
  @sides = 8
end

puts Polygon.sides # => 8

class Octogon < Polygon; end

puts Polygon.sides # => 8
puts Octogon.sides # => 8

Ref: http://railstips.org/2006/11/18/class-and-instance-variables-in-ruby

Its rather difficult to believe we must in each case define / require
our own custom module. Please note - i'm not complaining here. I just
want to know whether the above example is "the best solution in use"
for 1.8... 1.9....


Best regards,

dreamcat4
dreamcat4@gmail.com