From: Christoph Rippel <crippel@...>
Date: 2000-12-20T05:55:27+09:00
Subject: [ruby-talk:7715] Re: (Maybe) a correction for Programming Ruby

-----Original Message-----
From: dave@thomases.com [mailto:dave@thomases.com]On Behalf Of Dave Thomas
Sent: Tuesday, December 19, 2000 12:14 PM
To: ruby-talk ML
Subject: [ruby-talk:7710] Re: (Maybe) a correction for Programming Ruby

>      When this module is included in another, Ruby calls
>     \METHOD{append\_features} in this module, passing it the
>     receiving module in \obj{aModule}. Ruby's default implementation
>      is to add the constants, methods, and module variables of this
>      module to \obj{aModule} if this module has not already been
>     added to \obj{aModule} or one of its ancestors. See also...


I think this is fine except that Matz seems to have implemented ``instance
module variables'' versus 'Module variables' (see below). You did not fully
describe these concepts in your book (as far as I know) so it's probably okay
(and too late for now)  - well maybe it should be  ...

if this module has not already been included in \obj{aModule} or one of its
ancestors  ...  - but I have no strong opinions about this.





Christoph


module Mod
@inst                  # we could use attr.
@@mod = "m"
def ins
  @ins
end
def mod
  @@mod
end
end

class A
include Mod
def initialize
   @ins = "a"
end
end
class B
include Mod
def initialize
   @ins = "b"
end
end



a = A.new
b = B.new
a.ins == b.ins       # false
a.mod == b.mod  # true