Rails - Jun 2006 - Multiple belongs_to

Let''s say I have a catalog with hotels. Each hotel belongs to a
category (4-star, 5-star etc.) This is it''s official category.However,
there is also a category that users assign and a category that
"independent reviewers" assign. So I have this:

hotels {
  id,
  category_id,
  reviewer_category,
  user_category
}

categories {
  id,
  name
}

class Hotel < ActiveRecord::Base
    belongs_to :hotel_class # this is fine and ok

   # can I also something like this, however?
   belongs_to :hotel_class,
                    :foreign_key => ''reviewer_category''

   belongs_to :hotel_class,
                    :foreign_key => ''user_category''
end

I would really really really hate to do something like
HotelCategory.find(:first, :conditions => ...) for every hotel
request. I want ORM :)

What''s the approach to such a situation?

Thank you

Dmitrii Dimandt wrote:
> Let''s say I have a catalog with hotels. Each hotel belongs to a
> category (4-star, 5-star etc.) This is it''s official
category.However,
> there is also a category that users assign and a category that
> "independent reviewers" assign. So I have this:
> 
> hotels {
>   id,
>   category_id,
>   reviewer_category,
>   user_category
> }
> 
> categories {
>   id,
>   name
> }
> 
> class Hotel < ActiveRecord::Base
>     belongs_to :hotel_class # this is fine and ok
> 
>    # can I also something like this, however?
>    belongs_to :hotel_class,
>                     :foreign_key =>
''reviewer_category''
> 
>    belongs_to :hotel_class,
>                     :foreign_key => ''user_category''
> end
You can set up a separate association for each such foreign key, and 
specify the name of the key as part of the association. You should 
always use a name ending in _id for such foreign keys.

class Hotel < ActiveRecord::Base
  belongs_to :category
  belongs_to :reviewer_category,
    :class_name=> ''Category'', :foreign_key =>
''reviewer_category_id''
  belongs_to :user_category,
    :class_name=> ''Category'', :foreign_key =>
''user_category_id''
end

--
Josh Susser
http://blog.hasmanythrough.com

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

> You can set up a separate association for each such foreign key, and
> specify the name of the key as part of the association. You should
> always use a name ending in _id for such foreign keys.
>
> class Hotel < ActiveRecord::Base
>   belongs_to :category
>   belongs_to :reviewer_category,
>     :class_name=> ''Category'', :foreign_key =>
''reviewer_category_id''
>   belongs_to :user_category,
>     :class_name=> ''Category'', :foreign_key =>
''user_category_id''
> end
>
Thank you! I totally overlooked the :class_name thing.

Dmitrii Dimandt wrote:
> Thank you! I totally overlooked the :class_name thing.
Newbie clarification question:

If a model has multiple belongs_to references, you ahve to specify a 
class name and a foreign key?

I understand the foreign key, but what''s the logic behind specifying
the
class name? What does that do?



--
Austin

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

Austin Govella wrote:
> If a model has multiple belongs_to references, you ahve to specify a 
> class name and a foreign key?
> 
> I understand the foreign key, but what''s the logic behind
specifying the
> class name? What does that do?
Rails infers the class of the related object from the name of the field. 
So belongs_to :user_category will by default assume it is a UserCategory 
model, which is wrong. You override that default by setting the 
class_name option. Unfortunately setting the class_name also sets the 
foreign_key name, so you have to specify that explicitly as well. I 
believe in Rails 2.0 that will be changed so that it''s more DRY.

--
Josh Susser
http://blog.hasmanythrough.com

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