Rails - Feb 2008 - has_many association where the source model can be in several columns

Hello all,

I have an application dealing with User and Transaction objects, each
transaction going from a source user to a target user.

I have defined the following associations in user.rb :

has_many :transactions_as_source, :class_name => "Transaction", :as
=> :source
has_many :transactions_as_target, :class_name => "Transaction", :as
=> :target

and this is working fine, but I''m looking for a way to define
"has_many :transactions" to get all the transactions having the user
as a source *OR* a target, i.e. something like:

has_many :transactions, :finder_sql => ''SELECT * FROM transactions
WHERE source_id = #{id} OR target_id = #{id}''

but without resorting to finder_sql (as with this definition I cannot
cascade additional queries such as
current_user.transactions.sum(:amount) or
current_user.transactions.find(...).

Thanks,

Nicolas
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Hum, it looks like you are about to enjoy the has_many through 
polymorphism troubles...

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

My only personal advice will be : be VERY careful with each letter 
(specifically the "s") you will use because if it does not work Rails 
won''t say a word.

H

nj wrote:
> Hello all,
> 
> I have an application dealing with User and Transaction objects, each
> transaction going from a source user to a target user.
> 
> I have defined the following associations in user.rb :
> 
> has_many :transactions_as_source, :class_name =>
"Transaction", :as
> => :source
> has_many :transactions_as_target, :class_name =>
"Transaction", :as
> => :target
> 
> and this is working fine, but I''m looking for a way to define
> "has_many :transactions" to get all the transactions having the
user
> as a source *OR* a target, i.e. something like:
> 
> has_many :transactions, :finder_sql => ''SELECT * FROM
transactions
> WHERE source_id = #{id} OR target_id = #{id}''
> 
> but without resorting to finder_sql (as with this definition I cannot
> cascade additional queries such as
> current_user.transactions.sum(:amount) or
> current_user.transactions.find(...).
> 
> Thanks,
> 
> Nicolas
-- 
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