Rails - Apr 2007 - has_many :through polymorphic

Hi All,

I have the following arrangement:

class PickAndPackRequest < ActiveRecord::Base
  has_many :transactions, :as => :request
  has_many :postings, :through => :transactions
end

class Transaction < ActiveRecord::Base
  belongs_to :request, :polymorphic => true
  has_many :postings
end

class Posting < ActiveRecord::Base
  belongs_to :transaction
end

But when I ask for PickAndPackRequest.find(:first).postings.find(:all)
it fails with:

  Mysql::Error: Unknown column ''transactions.transaction_id''
in ''on
clause''

It generates the following SQL (which appears to be incorrect):

  SELECT postings.* FROM postings INNER JOIN transactions ON
postings.id = transactions.transaction_id WHERE
((transactions.request_id = 14) AND (transactions.request_type
''PickAndPackRequest''))

The "ON" clause appears to be wrong, I would have thought it would be:

    ON postings.transaction_id = transaction.id

Can anybody point out what I''m doing wrong, because I''m
stumped!

Cheers

Matthew.


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http://blog.hasmanythrough.com/2006/4/3/polymorphic-through

On 30/04/07, mhoroschun-Hqix5oD4n6s0n/F98K4Iww@public.gmane.org
<mhoroschun-Hqix5oD4n6s0n/F98K4Iww@public.gmane.org>
wrote:
>
>
> Hi All,
>
> I have the following arrangement:
>
> class PickAndPackRequest < ActiveRecord::Base
>   has_many :transactions, :as => :request
>   has_many :postings, :through => :transactions
> end
>
> class Transaction < ActiveRecord::Base
>   belongs_to :request, :polymorphic => true
>   has_many :postings
> end
>
> class Posting < ActiveRecord::Base
>   belongs_to :transaction
> end
>
> But when I ask for PickAndPackRequest.find(:first).postings.find(:all)
> it fails with:
>
>   Mysql::Error: Unknown column
''transactions.transaction_id'' in ''on
> clause''
>
> It generates the following SQL (which appears to be incorrect):
>
>   SELECT postings.* FROM postings INNER JOIN transactions ON
> postings.id = transactions.transaction_id WHERE
> ((transactions.request_id = 14) AND (transactions.request_type >
''PickAndPackRequest''))
>
> The "ON" clause appears to be wrong, I would have thought it
would be:
>
>     ON postings.transaction_id = transaction.id
>
> Can anybody point out what I''m doing wrong, because I''m
stumped!
>
> Cheers
>
> Matthew.
>
>
> >
>
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Thanks for the reply, however I''m pretty confident that this
isn''t the
case that is covered in that article.

The article is talking about "the other side of" a
polymorphic :through. That''s not what I''ve got. If I was
asking for
all the Requests of a Transaction (of which there are many kinds of
Request) then that would be "the other side" and could be solved as
suggested in the article.

Cheers

Matthew.

On May 1, 12:26 am, njmacin...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org
wrote:
> http://blog.hasmanythrough.com/2006/4/3/polymorphic-through
>
> On 30/04/07, mhorosc...-Hqix5oD4n6s0n/F98K4Iww@public.gmane.org
<mhorosc...-Hqix5oD4n6s0n/F98K4Iww@public.gmane.org> wrote:
>
>
>
> > Hi All,
>
> > I have the following arrangement:
>
> > class PickAndPackRequest < ActiveRecord::Base
> >   has_many :transactions, :as => :request
> >   has_many :postings, :through => :transactions
> > end
>
> > class Transaction < ActiveRecord::Base
> >   belongs_to :request, :polymorphic => true
> >   has_many :postings
> > end
>
> > class Posting < ActiveRecord::Base
> >   belongs_to :transaction
> > end
>
> > But when I ask for PickAndPackRequest.find(:first).postings.find(:all)
> > it fails with:
>
> >   Mysql::Error: Unknown column
''transactions.transaction_id'' in ''on
> > clause''
>
> > It generates the following SQL (which appears to be incorrect):
>
> >   SELECT postings.* FROM postings INNER JOIN transactions ON
> > postings.id = transactions.transaction_id WHERE
> > ((transactions.request_id = 14) AND (transactions.request_type >
> ''PickAndPackRequest''))
>
> > The "ON" clause appears to be wrong, I would have thought it
would be:
>
> >     ON postings.transaction_id = transaction.id
>
> > Can anybody point out what I''m doing wrong, because
I''m stumped!
>
> > Cheers
>
> > Matthew.

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