Rails - Mar 2006 - Table belongs_to either of two other tables?

Suppose I have a site about books and authors, and users can leave 
comments on either a book or an author.

I''d want to have a table called "comments", which could
belong to either
an author OR a book.

In my structure I wouldn''t be sure whether to include an
"author_id" or
a "book_id", or both.

What would be the best way to handle this relationship?

Thanks in advance for any help,

Jeff

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look at polymorphic associations in redgerails...

On Sunday, March 19, 2006, at 4:46 PM, Jeff Coleman
wrote:
>
>Suppose I have a site about books and authors, and users can leave
>comments on either a book or an author.
>
>I''d want to have a table called "comments", which could
belong to either
>an author OR a book.
>
>In my structure I wouldn''t be sure whether to include an
"author_id" or
>a "book_id", or both.
>
>What would be the best way to handle this relationship?
>
>Thanks in advance for any help,
>
>Jeff
>
>--
>Posted via http://www.ruby-forum.com/.
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Mikkel Bruun

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Thanks, that looks like just the thing!

Jeff

Mikkel Bruun wrote:
> look at polymorphic associations in redgerails...
> 
> On Sunday, March 19, 2006, at 4:46 PM, Jeff Coleman wrote:
>>What would be the best way to handle this relationship?
>>http://lists.rubyonrails.org/mailman/listinfo/rails
> Mikkel Bruun
> 
> www.strongside.dk    - Football Portal(DK)
> nflfeed.helenius.org - Football News(DK)
> ting.minline.dk      - Buy Old Stuff!(DK)

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

Am Sonntag, den 19.03.2006, 16:46 +0100 schrieb Jeff
Coleman:
> Suppose I have a site about books and authors, and users can leave 
> comments on either a book or an author.
> 
> I''d want to have a table called "comments", which could
belong to either
> an author OR a book.
> 
> In my structure I wouldn''t be sure whether to include an
"author_id" or
> a "book_id", or both.
> 
> What would be the best way to handle this relationship?
class Book < ActiveRecord::Base
  has_many :comments
end

class Author < ActiveRecord::Base
  has_many :comments
end

class Comment < ActiveRecord::Base
  belongs_to :book
  belongs_to :author
end

In your comments table include a book_id and an author_id field.

-- 
Norman Timmler

http://blog.inlet-media.de