From: Joel VanderWerf <vjoel@...>
Date: 2007-06-11T14:52:09+09:00
Subject: Re: Prettier solution to circular dependency

Helder Ribeiro wrote:
> This is an aesthetic problem: I have a method in a module, and I want
> to include it in three different classes (they're all in the same
> file). This method refers itself to one of those classes. So i have to
> include the module into the classes, but for the method to be parsed,
> one of those classes needs to be already defined.
> 

You can define the Element class at the top, and then reopen it later to 
include the module and define your methods. Just make sure that if 
Element is a subclass of something, the _first_ "class Element" must 
have the " < SuperClass". But in this case all you have to do is add 
these lines:

class Element
end

> module ElementFactory
>  def element_factory(what)
>    (...)
>    Element.new
>  end
> end
> 
> class Element
>  include ElementFactory
>  (...)
> end
> 
> class Document
>  include ElementFactory
>  (...)
> end
> 
> class ElementCollections
>  include ElementFactory
>  (...)
> end
> 
> 
> So for this class Element there's a circular dependency and, as ruby
> does single-pass parsing, this can't work. What I've done so far is to
> replace the explicit reference to Element in the module instance
> method by a call to Object.const_get(:Element) so that when it's
> called, Element will already be defined. But this looks a bit ugly.
> isn't there a better way to solve this?
> 
> The circular dependency hints at not having the module at all and just
> putting the instance method element_factory() into Element itself but
> there are those other two classes that include it, so I can't do that.
> 
> Thanks a lot for any ideas! :-)
> 
> 
> Cheers,
> 
> Helder
> 
> 


-- 
       vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407