On Aug 21, 11:29 am, Daniel Roseman <[EMAIL PROTECTED]>
wrote:
> On Aug 21, 4:42 pm, Brandon Taylor <[EMAIL PROTECTED]> wrote:
>
> > Hi everyone,
>
> > I have a column, 'position', which is a PositiveIntegerField, to allow
> > my end-user to order records with. I would like to pre-populate the
> > field when creating a new record, with the count of the model objects
> > + 1.
>
> > The models documentation says 'default' can be a value or a callable,
> > but using self.objects.count() + 1 doesn't work, because 'self' hasn't
> > been defined.
>
> > Can anyone point me to an example of how I can accomplish this?
>
> > TIA,
> > Brandon
>
> 'self.objects.count() + 1' isn't a callable, it's an expression, which
> you can't use here. (A callable is a function object, or a class with
> __call__ defined.)
> However, unfortunately even a callable probably wouldn't help you
> here, as the implementation calls it without any parameters. It's
> really just for things like inserting the current time, which doesn't
> need parameters.
> Seehttp://www.djangoproject.com/documentation/models/field_defaults/
>
> You can achieve what you want by overwriting save() on the model:
>
> def save(self):
> if not self.position:
> self.position = self.objects.count() + 1
> super(YourClassName, self).save()
>
> --
> DR.
Couldn' t why do you need a function with a parameter? Wouldn't a
function like this work:
class Widget(models.Model):
... some fields....
position = models.PositiveIntegerField(default=getNextPosition)
def getNextPosition():
return Widget.objects.count() + 1
Thanks,
John
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