Rails - Jan 2005 - Re: Taversing table relationships?

Trevor,

put belongs_to :sequence and belongs_to :location in your discovery class. Them
you can say something like @discovery.location.state.

If I remember correct, scaffolding doesn''t cover associations yet (but
it''s on the works) so you need to create your forms yourself. You can
use helpers like op
tions_for_select to create your select widgets (see the api docs for more info).

//jarkko


------- Original message -------
From: Trevor  <wenn0029-6BTuCrPg42A3uPMLIKxrzw@public.gmane.org>
Sent: 15.1.''05,  10:59
> Here are my three models:
> class Discovery < ActiveRecord::Base
> end
> 
> class Sequence < ActiveRecord::Base
>   has_many :discoveries
> end
> 
> class Location < ActiveRecord::Base
>   has_many :discoveries
> end
> 
> The ''discoveries'' table holds: id, location_id,
sequence_id, name, and notes
> 
> When doing the ''list'' part of the basic scaffolding, is
there a way to
> have the location_id and sequence_id columns fill in with the values 
> from the sequences and locations tables?
> 
> I can do it by hand (Location.find_first(discovery.location_id).state), 
> but I''m wondering if there would be a smoother way to do it.
> 
> It seems like it gets messy when using /views/discovery/edit.html as 
> well - I need to be able to provide a selectable list of available 
> ''sequences'' and ''locations''. 
What''s the Rails way of doing this?
> 
> Thanks,
> Trevor
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--
Jarkko Laine
http://jlaine.net
http://odesign.fi

Jarkko Laine wrote:
>put belongs_to :sequence and belongs_to :location in your discovery class.
Them you can say something like @discovery.location.state.
>  
>
Thank you Jarkko.  Very nice, works well. 

I was surprised to see that both:
class Discovery < ActiveRecord::Base
  belongs_to :sequence
  belongs_to :location
end

##and##

class Discovery < ActiveRecord::Base
  belongs_to :sequences
  belongs_to :locations
end

work just fine.

I got a little stuck on a NoMethodError "undefined method `state''
for
nil:NilClass", but then I realized one of my location_id ''s was
set to
null.  I''ll have to add in some error handling for this kind of
occurance.

_
_