From: Aaron Patterson <aaron@...>
Date: 2009-09-13T07:41:18+09:00
Subject: Re: choosing a module name at runtime


On Sep 12, 2009, at 3:26 PM, John Smirnoff wrote:

> My application chooses at runtime the input format of some data, for
> example :xml or :mysql. Then, the app instantiates a DataManager. The
> DataManager class should 'include' the appropriate Module (either
> DataIOXML or DataIOMySQL).
> I tried to use include in the initialize method of DataManager, but  
> that
> doesn't work.
> Can I include a module in the initialize method of the class? If yes,
> how?
> If no: Any other ways how I can choose the correct module to include  
> at
> runtime?

You want the "extend" method, not the "include" method:

module A
   def foo
     "A: foo"
   end
end

module B
   def foo
     "B: foo"
   end
end

class C
   def initialize which
     extend(which == :a ? A : B)
   end

   def metaclass; class << self; self end end
end

p C.new(:a).metaclass.ancestors
p C.new(:b).metaclass.ancestors

Hope that helps.

---
Aaron Patterson
http://tenderlovemaking.com