On 7/02/2013 5:04pm, Derek wrote:
I am trying to access the field(s) of a Child table while still inside
the save method of the Parent table.
Assuming that the many-to-many field in the Parent table is called
`m2m_field`, and the field I need to access in the Child table is
called `child_field`, what I have tried is this:
What I think you need in the Parent model is access to the "through"
table - say Parent_Child - which has a foreign key to both Parent and
Child called Parent_Child.parent and Parent_Child.child respectively.
Like this ...
class Parent(models.Model):
child = models.ManyToManyField('Child', through='Parent_Child')
#
..
def save(self, *args, **kwargs):
obj_qs = Parent_Child.objects.filter(parent=self)
# which gives you a query set to play with and extract obj
# or if you know the child object
# obj = Parent_Child.objects.get(parent=self, child=whatever)
# which gives you obj
# then ...
data_I_need = obj.thingummy
super(Parent, self).save(*args, **kwargs)
This is not necessarily the correct way to do things. I think there
might be Django shortcut but I'm not immediately familiar with it. I'd
have to read the query docs.
Mike
def save_model(self, request, obj, form, change):
# save object and the many-to-many data
obj.save()
# this does not work:
data_I_need = obj.m2m.all()[0].child_field
# nor does this:
data_I_need = Parent.objects.get(pk=obj.pk).m2m.all()[0].child_field
# in fact, length is 0, so no data in the set...
print len(Parent.objects.get(pk=obj.pk).m2m.all())
I know I am not grasping some key aspect of the problem; but I cannot
see what it is, and would appreciate any help with this problem!
Thanks
Derek
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