From: Phrogz <phrogz@...>
Date: 2007-12-12T06:15:11+09:00
Subject: Re: Class variables per subclasses, defined in the superclass

On Dec 11, 10:58 am, Gareth Adams <gareth.ad...@gmail.com> wrote:
> What I'm trying to do is have a per-subclass variable created by a class method
> on the super class (which is called from the subclass). Fun.

class Base
  @thing1 = "Base 1"
  class << self
    attr_accessor :thing1
    attr_reader   :thing2
  end
  def self.thing2=( val )
    @thing2 = "I am Thing2, and my value is '#{val}'"
  end
  self.thing2 = 'Base'
end

p Base.thing1, Base.thing2
#=> "Base 1"
#=> "I am Thing2, and my value is 'Base'"

# Set values for subclasses in the class...
class Bar < Base
  @thing1 = "Barthing1"
end
# ...or later
Bar.thing2 = "Barthing2"

p Bar.thing1, Bar.thing2
#=> "Barthing1"
#=> "I am Thing2, and my value is 'Barthing2'"

# But since class instance variables aren't shared
# the base class (and other subclasses) are unchanged
p Base.thing1, Base.thing2
#=> "Base 1"
#=> "I am Thing2, and my value is 'Base'"