Django do something when model instance created

Question

I'm looking to update a user's coin count in their profile whenever I create a promo code redemption object from a model.

Is there a method that runs when the object is created so I can update a field in the users profile from the promo code redemption model?

I tried init() but the arguments were no longer being filled in and saved in the model and I'm just looking to run extra code rather than adding custom fields.

I saw the signals file mentioned but wouldn't it be simpler to have it be done automatically through the model as a method?

class Promo_Code_Redemption(models.Model):
    user = models.ForeignKey(User, on_delete=models.CASCADE)
    amount = models.DecimalField(max_digits=9,decimal_places=2)
    date = models.DateTimeField(default=timezone.now)
    code = models.ForeignKey(Promo_Code, on_delete=models.CASCADE)
    code_text = models.TextField()
    revenue_type = "Promo code"

    def __str__(self):
        return self.code.code

Alexey Popov · Accepted Answer · 2020-10-01 05:54:08Z

3

You can override Promo_Code_Redemption save() method:

# recommended naming convention for 
# class names in python is UpperCaseCamelCase
class Promo_Code_Redemption(models.Model):
    ...
    
    def save(self, *args, **kwargs):
        # you can check if object just created by comparing "pk" attr to None
        # you can also use _state attr see doc link below
        is_created = self.pk is None

        super(Promo_Code_Redemption, self).save(*args, **kwargs)

        if is_created:
            # do something here
            print('is created')

Model _state attr

answered Oct 1, 2020 at 5:54

Alexey Popov

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