Rails - Jul 2006 - HABTM vs. using has_many :through

All,

I''ve heard recently about has_many :through as a necessary alternative 
to HABTM (when the join table has it''s own id column, say, in a legacy 
schema).  However, is the prevailing Rails wisdom now that one should 
use has_many :through in _all_ cases?

If so, why?

Thanks,
Wes

-- 
Posted via http://www.ruby-forum.com/.

Uber associationatire Josh Susser has written a much recommended article 
outlining the features and pros/cons of habtm and hmt: 
http://blog.hasmanythrough.com/articles/2006/04/20/many-to-many-dance-off.

 > However, is the prevailing Rails wisdom now that one should
 > use has_many :through in _all_ cases?
As with a lot of Rails wisdom the short answer is ''it depends''
:0)

Steve


Wes Gamble wrote:
> All,
> 
> I''ve heard recently about has_many :through as a necessary
alternative
> to HABTM (when the join table has it''s own id column, say, in a
legacy
> schema).  However, is the prevailing Rails wisdom now that one should 
> use has_many :through in _all_ cases?
> 
> If so, why?
> 
> Thanks,
> Wes
>

It may be heresy to some, but I still prefer HABTM over  
has_many :through if the relationship I''m dealing with is simple.   
i.e., if there''s no reason to store any metainfo in a join model, I  
just use HABTM.  I like my proxy collections!

This doesn''t mean I don''t love (and use) has_many :through for
situations when there does need to be metainfo stored about the  
relationship.  But I always ask myself first before I decide which to  
use.

-Seth

On Jul 10, 2006, at 12:25 AM, Wes Gamble wrote:
> All,
>
> I''ve heard recently about has_many :through as a necessary
alternative
> to HABTM (when the join table has it''s own id column, say, in a
legacy
> schema).  However, is the prevailing Rails wisdom now that one should
> use has_many :through in _all_ cases?
>
> If so, why?
>
> Thanks,
> Wes
>
> -- 
> Posted via http://www.ruby-forum.com/.
> _______________________________________________
> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
>
>

Agreed.

On 7/10/06, Seth Morabito <sethm@loomcom.com>
wrote:
>
> It may be heresy to some, but I still prefer HABTM over
> has_many :through if the relationship I''m dealing with is simple.
> i.e., if there''s no reason to store any metainfo in a join model,
I
> just use HABTM.  I like my proxy collections!
>
> This doesn''t mean I don''t love (and use) has_many
:through for
> situations when there does need to be metainfo stored about the
> relationship.  But I always ask myself first before I decide which to
> use.
>
> -Seth
>
> On Jul 10, 2006, at 12:25 AM, Wes Gamble wrote:
>
> > All,
> >
> > I''ve heard recently about has_many :through as a necessary
alternative
> > to HABTM (when the join table has it''s own id column, say, in
a legacy
> > schema).  However, is the prevailing Rails wisdom now that one should
> > use has_many :through in _all_ cases?
> >
> > If so, why?
> >
> > Thanks,
> > Wes
> >
> > --
> > Posted via http://www.ruby-forum.com/.
> > _______________________________________________
> > Rails mailing list
> > Rails@lists.rubyonrails.org
> > http://lists.rubyonrails.org/mailman/listinfo/rails
> >
> >
>
> _______________________________________________
> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
>
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Wes Gamble wrote:
> All,
> 
> I''ve heard recently about has_many :through as a necessary
alternative
> to HABTM (when the join table has it''s own id column, say, in a
legacy
> schema).  However, is the prevailing Rails wisdom now that one should 
> use has_many :through in _all_ cases?
Not at all.

Think about the model first. Do you want to model your associations 
explicitly, using a model class? In other words, are there things that 
you want to say about the associations? (Can you put a name to them? 
This may help you to find things that you might want to say about them.) 
If so, use a model for the association... and then you will need the 
:through capability to let you navigate through the association in a 
single query.

If you just want the association to exist, with nothing further being 
said about it, stick with HABTM.

In other words, I agree with others in this thread, but would like to 
put the emphasis on thinking carefully about the domain model.

regards

   Justin