Rails - Jun 2005 - observing a habtm association

Is there some way to observe when an association is added in a habtm
relationship?

I know I could turn the relationship into a model, but I don''t want to
give up using
:include in my finds...

joshua

On 6/25/05, Joshua <joshua-q0Yur7km1XpBDgjK7y7TUQ@public.gmane.org>
wrote:
> Is there some way to observe when an association is added in a habtm
> relationship?
I was able to achieve this, but I had to create a method on one of my
models.  It basically called some custom methods in the observer.  It
went something like this:

# in the model...
def Auction.add_bid(bid)
  self.class.changed
  self.class.notify_observers(:before_add_bid, self, bid)
  self.bids << bid
end

# in the observer...
class AuctionObserver < ActiveRecord::Observer
  # needed to override ActiveRecord::Observer#update
  def new_update(callback_method, object, bid = nil)
    if bid
      send(callback_method, object, bid) if respond_to?(callback_method)
    else 
      old_update(callback_method, object)
    end
  end
  alias_method :old_update, :update
  alias_method :update, :new_update

  def before_add_bid(record, bid)
  end
end

Obviously, you can''t use the simple @model.items << @item syntax
anymore, but for me it was an ok tradeoff.  If anyone has a better
idea, let me know!


-- 
rick
http://techno-weenie.net

Rick Olson wrote:
># in the model...
>def Auction.add_bid(bid)
>  self.class.changed
>  self.class.notify_observers(:before_add_bid, self, bid)
>  self.bids << bid
>end
>
>
>Obviously, you can''t use the simple @model.items << @item
syntax
>anymore, but for me it was an ok tradeoff.  If anyone has a better
>idea, let me know!
>  
>
Thanks!

It seems like there should be a way of just overriding << for the 
associations array, but I haven''t figured that one out,
and it''s a pretty minor inconvenience.

joshua