I am writing the pre_save method to create the slug for model, for some reason my instance is none.
@receiver(pre_save, sender=Employee)
def pre_save_employee_receiver(sender, instance, *args, **kwargs):
slug = slugify(" ".join([instance.name, instance.surname, instance.id]))
instance.slug = slug
Error is:
File "E:\Work\hire_handler\employees\models.py", line 60, in pre_save_employee_receiver
slug = slugify(" ".join([instance.name, instance.surname, instance.id]))
TypeError: sequence item 2: expected str instance, NoneType found
No , the instance
is not None
, the primary key ( instance.id
) is None
.
That makes perfect sense, before creating the object at the database side, the item has no primary key, since database dispatches a primary key.
If you thus want to work with a primary key, you need to work with a post_save
item, furthermore likely the id
is an int, so it will still not work, since ' '.join()
can not join integers.
You can use a post_save
trigger, and save it again, but that will result in making two queries when you create a new Employee
:
@receiver(post_save, sender=Employee)
def post_save_employee_receiver(sender, instance, created, *args, **kwargs):
if :
instance.slug = slugify(f'{instance.name} {instance.surname} {instance.pk}')
instance
Furthermore signals are usually a bit of an antipattern , especially since when you for example perform .bulk_create()
, .update()
, etc. the signals are not triggered.
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