On Aug 24, 3:36 pm, Tom Evans <[email protected]> wrote: > On Tue, Aug 23, 2011 at 11:28 PM, ernando <[email protected]> wrote: > > Hi all, > > > maybe it's newbie question but I wasn't able to find clear answer/ > > solution on it. > > > For example, we have the following models: > > > class A(models.Model): > > id = models.AutoField(primary_key=True) > > title = models.CharField(max_length=30) > > > class B(models.Model): > > id = models.AutoField(primary_key=True) > > title = models.CharField(max_length=30) > > aItems = models.OneToOneField(A) > > > And try to save them in the following way: > > > a = A(title="123") > > b = B(title="333", aItems = a) > > b.save() > > > This code runs with the error: (1364, "Field 'aItems_id' doesn't have > > a default value") > > if I firstly save a object - everything goes smoothly. So, the > > question is - should we always save all related objects manually? > > According to django docs we have to create object at first. But that's > > now always convenient - e.g. I receive full model from the 3rd part > > service and want to save it into DB with one call and not do it for > > each item. > > > Regards, > > Dmitry > > Only objects that exist in the database can be related to each other. > If you have a function which accepts an model instance, it should make > it clear that it is an error to pass it an object that does not exist > in the database. You really should not be overriding save() to save > related objects that do not exist in the database. > > Mostly these kind of problems go away if you start using the create > and get_or_create helpers on the model's manager, eg I would never > have this in my code: > > a = A(title="123") > b = B(title="333", aItems = a) > b.save() > > it would look like this: > > a, created = A.objects.get_or_create(title='123') > b = B.objects.create(title='333', aitems=a) > > Cheers > > Tom
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