Smart One-To-One Field

For Django

django-smartonetoonefield provides utility fields discussed in this Fusionbox blog post

Compatibility

• Python: >= 3.12
• Django: >= 4.2

Installation

1. Install the latest version:

   pip install django-smartonetoonefield

   poetry add django-smartonetoonefield

2. Add smartonetoonefield to INSTALLED_APPS in your project's settings.py.

Usage

AutoOneToOneField

If you can create a related model by just filling in one field, then AutoOneToOneField will simplify your code.

To use, define an AutoOneToOneField field on a model with a relation to another field. This will ensure that the related model object will always exist, even if it must be created upon first access.

models.py:

class CustomerProfile(models.Model):
    user = AutoOneToOneField('User', related_name='customer_profile')

user = User.objects.all()[0]
user.customer_profile  # Always returns a customer profile

SoftOneToOneField

If you cannot create the related model by simply setting the foreign key on the related model, then a SoftOneToOneField might work better for you.

With SoftOneToOneField, if the related model object exists, the lookup will work as normal. But if the related model object does not exist, then the attribute will be None.

models.py:

class CustomerProfile(models.Model):
    user = SoftOneToOneField('User', related_name='customer_profile')

views.py:

class MyProfileView(DetailView):
    def get_context_data(self, **kwargs):
        kwargs = super(MyProfileView, self).get_context_data(**kwargs)
        # This will not raise an exception if the customer_profile does
        # not exist
        kwargs.update(my_profile=self.customer_profile)
        return kwargs

AddFlagOneToOneField

Sometimes, when you need to check if a related model exists or not, it can be unwieldy to query the relation directly. A workaround to this is to define properties on the reverse related model:

models.py:

class User(AbstractUser):
    # ...
    def is_customer(self):
        return hasattr(self, 'customer_profile')


class CustomerProfile(models.Model):
    user = models.OneToOneField('User', related_name='customer_profile')

However, this can necessitate creating a custom default user model for a project, and this can be impossible if you need to override a model in a third party Django app.

Instead of overriding models or querying the related fields directly, the AddFlagOneToOneField will automatically add flags to the related model to make it easier to query related fields:

models.py:

class CustomerProfile(models.Model):
    user = AddFlagOneToOneField('auth.User', related_name='customer_profile',
                                flag_name='is_customer')


class MerchantProfile(models.Model):
    user = AddFlagOneToOneField('auth.User', related_name='merchant_profile',
                                flag_name='is_merchant')


class EmployeeProfile(models.Model):
    user = AddFlagOneToOneField('auth.User', related_name='employee_profile',
                                flag_name='is_employee')

views.py:

user = User.objects.get(email='customer@example.com')
user.is_customer  # True
user.is_merchant  # False
user.is_employee  # False

Since the AddFlagOneToOneField won't throw exceptions on access, you don't have to override, inherit, or modify other models when using the specified flags.

TODO

I have intentionally kept this app very small to minimize the maintenance burden. But contributions are very welcome!

License

BSD