On Saturday 25 July 2009, Emma wrote:
> I'm having trouble with this model:
>
> class Person < AR::B
> belongs_to :shipping_address, :class_name => 'Address'
> belongs_to :billing_address, :class_name => 'Address'
> end
>
> class Address < AR::B
> end
>
> The problem is that I want Address to be a Value Object (as in DDD),
> and if I do this:
> p = Person.create :shipping_address => Address.new(...)
>
> and later I change the address:
> p.shipping_address = Address.new(...)
> p.save
>
> the first address object doesn't get deleted from the DB. It becomes
> an orphan.
I'd try to handle a case like this in a callback. ActiveRecord
automatically generates methods like #shipping_address_id_changed?, but
that does only half the job in this particular case, because assigning
an unsaved object (such as Address.new) to a belongs_to association does
not change the existing foreign key immediately.
class Person < AR::B
belongs_to :shipping_address, :class_name => 'Address'
belongs_to :billing_address, :class_name => 'Address'
protected
def before_save
if shipping_address_id_changed? ||
shipping_address && (shipping_address_id != shipping_address.id)
Address.delete(shipping_address_id_was) if shipping_address_id_was
end
# same for billing_address; better extract the common code
end
end
The code probably won't work as is, but it might get you started. Also,
have a look at the :autosave option for belongs_to.
HTH,
Michael
--
Michael Schuerig
mailto:[email protected]
http://www.schuerig.de/michael/
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