Check if OneToOneField is None in Django

Question

I have two models like this:

class Type1Profile(models.Model):
    user = models.OneToOneField(User, unique=True)
    ...


class Type2Profile(models.Model):
            


        

Answer 1

One of the smart approaches will be to add custom field OneToOneOrNoneField and use it [works for Django >=1.9]

from django.db.models.fields.related_descriptors import ReverseOneToOneDescriptor
from django.core.exceptions import ObjectDoesNotExist
from django.db import models


class SingleRelatedObjectDescriptorReturnsNone(ReverseOneToOneDescriptor):
    def __get__(self, *args, **kwargs):
        try:
            return super().__get__(*args, **kwargs)
        except ObjectDoesNotExist:
            return None


class OneToOneOrNoneField(models.OneToOneField):
    """A OneToOneField that returns None if the related object doesn't exist"""
    related_accessor_class = SingleRelatedObjectDescriptorReturnsNone

    def __init__(self, *args, **kwargs):
        kwargs.setdefault('null', True)
        kwargs.setdefault('blank', True)
        super().__init__(*args, **kwargs)

Implementation

class Restaurant(models.Model):  # The class where the one-to-one originates
    place = OneToOneOrNoneField(Place)
    serves_hot_dogs = models.BooleanField()
    serves_pizza = models.BooleanField()

Usage

r = Restaurant(serves_hot_dogs=True, serves_pizza=False)
r.place  # will return None