From: Ragav Satish <ragavsatish@...>
Date: 2008-10-04T17:10:55+09:00
Subject: Re: module scope not clear to me

Nit Khair wrote:
> I had a program which inherits from a superclass. It also has
> common/convenience methods in a module.
> 
> <code>
>  require 'common'
>  include 'Common'
>  class Prog < Application
>     f = Obj.new
>     g = Foo.new
>     #... etc ...
> </code>
> 
> 
> Some convenience methods rely on a variable being set in the superclass.
> (I know that does not sound good but it shields this detail from
> individual programs.)
> 
> Then i refactored ... moved a lot of functionality out from the program
> to objects it was creating. I would guess that these objects should
> _not_ be able to call the module methods. Suprisingly, they were.
> 
> The problem came up that the variable was obviously not set when called
> by these objects, (since the class of the module was now the object's
> class not the program's class.)
> 
> So my basic question is: if a program includes a module, can all its
> composed objects also call on the module.

Depends on where the module is included. If its included at the top 
level (outside of another class/module) then it's mixed into the Object 
class from which all other classes ultimately derive , so method lookup 
on any object will always find it.

    module M
      def foo; puts "module foo" end
    end

    class C; end
    # method name resolution chain before include
    p C.ancestors #=> [C, Object, Kernel]

    include M     # including at top level has M as the

    p C.ancestors #=> [C, Object, M, Kernel]

    C.new.foo     #=> module foo

    # heck you can even call it on "M", "C" since they are also objects
    M.foo   #=> module foo
    C.foo   #=> module foo.

Once you include a module at the *top level* you are creating a set of 
methods accessible from anywhere.

--Cheers
--Ragav
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