From: ts <decoux@...>
Date: 2001-12-28T15:56:04+09:00
Subject: [ruby-talk:29514] Re: Module#included

>>>>> "B" == Bob Hutchison <hutch@xampl.com> writes:

 Well, the response was given by Nobu Nakada. Just a small example

B> Is there a recommended way to obtain some data from the new module (the one
B> including this module). For example, I'd like to set up a hash that maps a
B> string to the new module, but only if it is defined. The trouble is that I
B> cannot use the included module to define default values (it seems, and this
B> is why I think the method is called before the module is included). I am
B> forced to trap an exception if the string is not defined in the new module
B> -- this works, but...

 Here a stupid example which define an instance variable (if it's not
 defined) in the class which make the include 

pigeon% cat b.rb
#!./ruby
module M
   def self.included klass
      klass.class_eval do
         @data ||= M
         class << self
            attr_reader :data
         end
      end
   end
end

class C
   include M
end

p C.data

class D
   @data = C
   include M
end

p D.data
pigeon% 

pigeon% b.rb
M
C
pigeon% 

B> What can you do in the included method? Can you affect how things are
B> included? or is this simply an interesting event?

 Like it was said previously ::included is called after ::append_features.
 I'll say that

  ::append_features can affect how things are included
  ::included is an interesting event that you can use after the include is
  made. 



Guy Decoux