I'm using Django 2.1.5.
There is a model with 'auto_now' field:
class BaseModel(models.Model):
id = models.UUIDField(default=uuid.uuid4, editable=False, db_index=True, unique=True, primary_key=True)
updated_at = models.DateTimeField(db_index=True, auto_now=True)
updated_by = models.CharField(max_length=200)
responded_at = models.DateTimeField(db_index=True, null=True, blank=True)
responded_by = models.CharField(max_length=200, null=True, blank=True)
Now, I have a pre_save
signal for that model, and I want to update there the responded_at
and responded_by
fields to be equal to updated_at
and updated_by
. In that signal - the updated_by
value is already the new one, as supposed to be in the end of the request, but the updated_at
is not. It's the old (current) value. I want, if possible, to be able to get the value that supposed to be in updated_at
field after the save.
The reason I'm using pre_save
signal and not post_save
is because I'm updating the instance inside it.
Since your are using auto_now
with your updated_at
field, it will inherit editable=False
and blank=True
.
As the docs state:
As currently implemented, setting auto_now or auto_now_add to True will cause the field to have editable=False and blank=True set.
To avoid this, you can write a custom field like this:
from django.utils import timezone
class AutoDateTimeField(models.DateTimeField):
def pre_save(self, model_instance, add):
return timezone.now()
You can use this in your BaseModel
like this:
class BaseModel(models.Model):
updated_at = models.AutoDateTimeField(default=timezone.now)
# ...
This way the updated_at
field should be editable and your signal should work.
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