How to create auto add ShortUUIDField in Django-CodePudding

I need to create a django ShortUUIDField that automatically generate the value when the entry is created:

Here's my code:

def generate_short_uuid():
    string_uuid = str(uuid.uuid4())
    return string_uuid.replace('-', '')[:12]


class ShortUUIDField(models.CharField):
    def __init__(self, *args, **kwargs):
        kwargs['default'] = generate_short_uuid
        kwargs['editable'] = False
        kwargs['unique'] = True
        kwargs['blank'] = True
        kwargs['null'] = True
        kwargs['max_length'] = 12

        super().__init__(*args, **kwargs)

    def pre_save(self, model_instance, add):
        if add:
            while True:
                try:
                    value = generate_short_uuid()
                    setattr(model_instance, self.attname, value)
                    return value
                except IntegrityError as e:
                    if 'duplicate key' in str(e):
                        continue
                    raise

Here's the model that use the field:

class UserProfile(models.Model):
    uuid = ShortUUIDField()
    user = models.OneToOneField("users.User", on_delete=models.CASCADE, related_name="profile")

Here's the error that occurs when I try to create the entry:

django.db.utils.IntegrityError: null value in column "uuid" of relation "profiles_userprofile" violates not-null constraint

CodePudding user response：

The error you're seeing is because the uuid field in the UserProfile model is defined as a ShortUUIDField, which you've set to have a default value of the generate_short_uuid function. However, when you create a new UserProfile instance and don't explicitly set a value for the uuid field, the default value is None, which is not a valid value for the ShortUUIDField.

One way to fix this issue is to change the default value of the ShortUUIDField to generate_short_uuid() instead of the generate_short_uuid function. This way, when the field is instantiated, the default value will be the return value of the function (i.e. a new short UUID), rather than the function itself.

CodePudding user response：

you can use the ShortUUIDField from the shortuuidfield library to create a field that automatically generates a short universally unique identifier (UUID) for each instance of a model.

First, you'll need to install the shortuuidfield library using pip:

pip install django-shortuuidfield

from django.db import models
from shortuuidfield import ShortUUIDField

class MyModel(models.Model):
    id = ShortUUIDField(primary_key=True)