Created Field(DateTimeField) auto_now_add=True is not working in Abstract Class in Django

Question

class TimeStampMixin(models.Model):
    id = models.CharField(max_length=60,editable=False,primary_key=True,default=generate_unique_id)
    created = models.DateTimeField(editable=False)
    modified = models.DateTimeField(auto_now=True)
    
    def save(self, *args, **kwargs):
        if not self.id:
            print("SAVING WHILE CREATE")
            self.created = timezone.now()
        
        print("MODIFY WHILE UPDATE")
        self.modified = timezone.now()
        return super().save(*args, **kwargs)


    class Meta:
        abstract = True

class Sport(TimeStampMixin):
    name = models.CharField(max_length=100, unique=True)
    image = models.ImageField(upload_to=path_and_rename,null=True,blank=True)
        
    def __str__(self):
        return self.name

    def save(self, *args, **kwargs):
        self.name = self.name.upper()
        return super(Sport, self).save(*args, **kwargs)

Explaination I have created an abstract model TimeStampMixin with custom save method. Then i have inherited from TimeStampMixin model to Sport Model. Now whenever i'm creating Sport object it raising django.db.utils.IntegrityError: null value in column "created" of relation "events_sport" violates not-null constraint DETAIL: Failing row contains (id, Test, image,2022-04-10 13:30:00+00, 2022-04-10 14:30:00+00, 2022-04-10 12:00:00+00).

Also Custom save method from timestampmixin not called. (Not print Anything).

Solution I need: While updating an object created field is also get updated. auto_now_add=True in datetimeField attribute is not working!!. How to prevent this?

Answer 1

I have reset the database and use this code

class TimeStampMixin(models.Model):
    id = models.CharField(max_length=60,editable=False,primary_key=True,default=generate_unique_id)
    created = models.DateTimeField(auto_now_add=True)
    modified = models.DateTimeField(auto_now=True)

    class Meta:
        abstract = True

Than its working fine for me!

Answer 2

Try if self._state.adding: instead of if not self.id:.

Note: if you use auto_now, you can't set new value for this field. Following document "it’s not just a default value that you can override." https://docs.djangoproject.com/en/3.2/ref/models/fields/#django.db.models.DateField.auto_now