How to use UUID

Question

I am trying to get unique IDs for my Django objects. In Django 1.8 they have the UUIDField. I am unsure how to use this field in order to generate unique IDs for each object in my model.

Here is what I have for the UUIDField

import uuid
from django.db import models

class MyUUIDModel(models.Model):
    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)

class Person(models.Model):
    ...
    unique_id = MyUUIDModel()

I can reproduce the id for the UUID model, but everytime I do I get the exact same id. For Example:

person = Person.objects.get(some_field = some_thing)
id = person.unique_id.id

id then gives me the same id every time. What is wrong, how do I fix this?

Answer 1

I'm not sure why you've created a UUID model. You can add the uuid field directly to the Person model.

class Person(models.Model):
    unique_id = models.UUIDField(default=uuid.uuid4, editable=False, unique=True)

Each person should then have a unique id. If you wanted the uuid to be the primary key, you would do:

class Person(models.Model):
    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)

Your current code hasn't added a field to the person. It has created a MyUUIDModel instance when you do MyUUIDModel(), and saved it as a class attribute. It doesn't make sense to do that, the MyUUIDModel will be created each time the models.py loads. If you really wanted to use the MyUUIDModel, you could use a ForeignKey. Then each person would link to a different MyUUIDModel instance.

class Person(models.Model):
    ...
    unique_id = models.ForeignKey(MyUUIDModel, unique=True)

However, as I said earlier, the easiest approach is to add the UUID field directly to the person.

Answer 2

You need to use the class you created as a subclass when declaring your Person model like this:

import uuid
from django.db import models

class MyUUIDModel(models.Model):
  id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)

class Person(MyUUIDModel):
  ...

This way Person becomes a subclass of MyUUIDModel and will inherit its id field definition.

Answer 3

EDIT: Actually I was wrong. It's not possible yet to implement it as DEFAULT_AUTO_FIELD as it has to inherit from IntegerField. Here's the ticket in the django project with feature request to make it possible. Once it's resolved I'll update my answer.

---

As of Django 3.2, if you want to use uuid as a pk for all your models on a project-wide level, you don't need a generic abstract model anymore. Just define DEFAULT_AUTO_FIELD setting

default value

DEFAULT_AUTO_FIELD = 'django.db.models.AutoField'

so something like this should work

DEFAULT_AUTO_FIELD = 'django.db.models.UUIDField'

Or even better, create your own field.

DEFAULT_AUTO_FIELD = 'project.common.models.CustomUUIDField'

Where you also define uuid type etc.

As seen in the docs, it can also be applied on an app level.

class MyAppConfig(AppConfig):
    default_auto_field = 'project.common.models.CustomUUIDField'