Rails - Jan 2007 - help with extensions

I am working with extensions to has_many associations, and I want to create
a finder method that is conditional on the attributes of the object whose
association I''m working with.

So, to use the example from the Agile Web Development: the authors show on
pg 340 in the second edition how to pass an argument to a finder method. But
I want to know if it''s possible to instead have the finder method look
at
attributes of the object on which the finder method is ultimately being
executed (here, user) to determine the conditions.

class User

  has_many :reading
  has_many :articles, :through => :readings do
    def rated_at_or_above(rating)                   # this is the finder
method in AWD -- works fine
        find :all, :conditions => [''rating >= ?'',
rating]
    end
    def rated_at_or_above_threshold               # but can I do something
like this? (doesn''t work)
        find :all, :conditions => [''rating >= ?'',
user.threshold]  #
NoMethodError: undefined method user for Article:class
    end
  end
end

How would I implement this? As the error suggests, the problem is that the
article doesn''t know who its user is. So how can I pass that
information to
this method, given that it''s nested inside of this association?

Thanks.

(Btw, I tried to post this yesterday but it has not appeared, and another
msg suggested that posts made from the Google Groups page get lost sometimes
-- sorry if this is double-posted.)

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Andy Eggers wrote:
> class User
> 
>   has_many :reading
>   has_many :articles, :through => :readings do
>     def rated_at_or_above(rating)                   # this is the finder
> method in AWD -- works fine
>         find :all, :conditions => [''rating >= ?'',
rating]
>     end
>     def rated_at_or_above_threshold               # but can I do 
> something
> like this? (doesn''t work)
>         find :all, :conditions => [''rating >= ?'',
user.threshold]  #
> NoMethodError: undefined method user for Article:class
>     end
>   end
> end
> 
> How would I implement this? As the error suggests, the problem is that 
> the
> article doesn''t know who its user is. So how can I pass that
information
> to
> this method, given that it''s nested inside of this association?
The code in an association extension is executed in the context of the 
AssociationProxy object, not the ActiveRecord model. Simply put, that 
means that "self" in the extension isn''t the user,
it''s the has_many
proxy. But proxy_owner points to the user, so you can do 
`proxy_owner.threshold` to get the user''s threshold.

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

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

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