From: Marcus Andersson <m-lists@...>
Date: 2006-06-29T06:26:00+09:00
Subject: Re: How to model Hibernate multi-table inheritance with ActiveRecord?

So far I have two solutions:

1) implement method_missing in Asset and delegate to [other]Asset where 
Asset cannot handle the requested method
2) implement method_missing in [other]Asset and delegate back to Asset 
where [other]Asset cannot handle the request (or a variant thereof)

1) gives easy querying (I can just query Asset for all objects) but I 
cannot override methods from Asset in [other]Asset. Not really good. 
This solution could be good if I could somehow make Asset ask 
[other]Asset if they have the requested method before calling the method 
in itself instead? Sort of like a default before handler on every method.
2) In order for this to work I always need to work on instances of 
[other]Asset. That in turns mean that I either have to make the query on 
[other]Asset class to get instances of [other]Asset or make the query on 
Asset and then start off by getting the [other]Asset instance from it 
and work with that (ie using Asset.find(:all).map(&:delegate_asset)). 
Neither of them feels really polymorphic. A solution here would be if 
one could bend ActiveRecord to return [other]Asset instead of Asset 
instances when querying the Asset class. I suppose this would be the 
solution to multi table inheritance though if I could solve it...

What I'm after is a solution to make it transparet for the clients of 
the Asset class (and associates). I don't care how much/ugly code I have 
to hide in Asset to just make it transparent to the clients (since I 
have control over Asset, not over the clients).

Have I missed anything? 2) sounds easy and good but I can't grip the 
querying situation (beyond what I described above). Have I missed 
something there?

Thanks for the answers.

/Marcus