Django model fields unique=True and default=function

Question

So I have a model that looks like this

def create_invite_code():
  return str(uuid.uuid4())[0:8]

class InviteCodes(models.Model): 
  id = models.CharField(max_length = 36, primary_key = True, default=build_uuid)      
  code = models.CharField(max_length=8, unique=True, default=create_invite_code)

What happens if create_invite_code returns a code that already exists in the db, will django call the function again until it finds one that doesn't exist? Or will it error out?

Answer 1

As people said here, it will raise "UNIQUE constraint failed" integrity error. Which could potentially happen cause you're not doing any check for uniqueness.

I would recommend django-uuidfield by David Cramer. It handles all the validation for you.

https://github.com/dcramer/django-uuidfield

Answer 2

The code field in your model InviteCodes is a unique field. If you tries to create another entry with an already existing code, then python will raise IntegrityError: UNIQUE constraint failed exception.

You can test it by returning a constant string from create_invite_code function. For example,

def create_invite_code():
  return 'test'

The first entry will be unique, but in the second call the exception will be raised.