On Sep 24, 12:52 am, "Daniele Procida" <dani...@apple-juice.co.uk>
wrote:
> Don't I need to run some sort of save for those? Otherwise, what happens
> to the attributes once I have set them?
Sorry, I responded too hastily and erroneously. Here's the proper,
longer explanation.
Assume the following models:
class Referee(models.Model):
name = models.CharField(max_length=255)
class Referrer(models.Model):
name = models.CharField(max_length=255)
references = models.ManyToManyField(Referee)
It is evident that a many-to-many relation (references) can be saved
only after the object that has the relation (Referrer) is warranted
to have a value for it's primary key field, as "behind the scenes,
Django creates an intermediary join table to represent the many-to-
many
relationship" (quote from
http://docs.djangoproject.com/en/dev/ref/models/fields/#manytomanyfield
)
So, given a obj = Referrer("foo"), updating its many-to-many field can
happen only after obj.save() returns (this is documented in
http://www.djangoproject.com/documentation/models/many_to_many/ ).
If you are not able to call obj.save() and then manually update the
fields, the only chance is to use a signal. Unfortunately, Django core
does
not currently fire any signals on ManyToManyField changes.
There's a ticket, http://code.djangoproject.com/ticket/5390 , that has
a
patch with a solid implementation of that particular signal. It also
includes
tests that demonstrate how to use the signal (see
http://code.djangoproject.com/attachment/ticket/5390/complete-patch.diff
).
So, unless the manual way works for you, I recommend you apply the
patch.
--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Django users" group.
To post to this group, send email to django-users@googlegroups.com
To unsubscribe from this group, send email to
django-users+unsubscr...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/django-users?hl=en
-~----------~----~----~----~------~----~------~--~---
