From: James Coglan <jcoglan@...>
Date: 2008-09-03T17:35:23+09:00
Subject: Re: How can I prevent include one module multi-times?

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2008/9/3 Sebastian Hungerecker <sepp2k@googlemail.com>

> Roger Pack wrote:
> > Zhao Yi wrote:
> > > I am looking for a method to check whether this module has been
> > > included. Does Ruby have this feature?
> >
> > Might try parsing Object.constants for the module name.
>
> Why? That only tells you whether that module exists (and it only tells you
> that when the module is in the top-level namespace). It doesn't tell you
> whether that module has been included into anything.



Ah, I think I misunderstood the question. I wrote this a while ago to find
all the descendants of a module:

class Module
  def descendants
    classes = []
    ObjectSpace.each_object do |klass|
      next unless Module === klass
      classes << klass if self > klass
    end
    classes
  end
end

So, a module has been included if

mod.descendants.size.nonzero?

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