Django how to add a field to a model that relies on the pk being created first-CodePudding

I am trying to add a hashid that is based on the pk of my model

class ExampleModel(models.Model):
    hash_id = models.CharField(max_length=30)

How the hash_id is created.. Assume 15454 is the pk of my object.

from hashids import Hashids
hashids = Hashids(salt='example salt')
hashids.encode(15454)
'Eo6v'

The main reason I want to store the hash_id in the model is because I don't want to recompute it everytime or if my salt changes in the future for some reason.

Is there a way to automatically generate this field when the object is created since it needs the PK to be created first?

CodePudding user response：

How about to override in save model? like:

class ExampleModel(models.Model):
    hash_id = models.CharField(max_length=30)

    def save(self, *args, **kwargs):
        is_create = self.pk is None
        super().save(*args, **kwargs)

        # We got pk after save above.
        if is_create:
            hashids = Hashids(salt='example salt')
            self.hash_id = hashids.encode(self.pk)
            super().save(update_fields=["hash_id"])