使（和测试）2 个字段在 Django 模型中是唯一的

Question

I have a model UserSite. Every User could have multiple sites. I now have to make them unique. So a site can't be added to a user if it already is appointed to that user. My Model code is:

class UserSite(models.Model):
    user = models.ForeignKey(User, on_delete=models.CASCADE, related_name="sites")
    site = models.ForeignKey(Site, on_delete=models.CASCADE, related_name="users")

    class Meta:
        unique_together = ("user", "site")

All fine. Now I want to make a test class who tests if this works. My test class:

from rest_framework.test import APITestCase

from models import UserSite
from factories import SiteFactory
from factories import UserFactory


class TestUniqueUserSite(APITestCase):
    def setUp(self):
        self.user = UserFactory()
        self.test_site = SiteFactory()
        self.test_site_2 = SiteFactory()

        self.user_site = UserSite.objects.create(user=self.user, site=self.test_site)

    def test_user_site_is_unique(self):
        """
        Check if a new UserSite is unique
        """
        self.user_site1 = UserSite.objects.create(user=self.user, site=self.test_site)

Factory:

class UserSiteFactory(factory.django.DjangoModelFactory):
    class Meta:
        model = UserSite

    # Type hinting
    def __new__(cls, *args, **kwargs) -> "UserSiteFactory.Meta.model":
        return super().__new__(*args, **kwargs)  # pragma: no cover

    site = factory.SubFactory(SiteFactory)
    user = factory.SubFactory(UserFactory)
    user_role = factory.fuzzy.FuzzyChoice(UserSite.USER_ROLE_CHOICES)

This test gives no errors, the UserSite can be created. What do I wrong? The testing or the unique field? or both hehe, thanks!

When I run:

UserSite.objects.filter(user=self.user, site=self.test_site).all()

I got:

<QuerySet [<UserSite: pk: 1 - user_pk: 1 - site_pk: 1>, <UserSite: pk: 2 - user_pk: 1 - site_pk: 1>]>

So they are stored..

Answer 1

我的猜测是 unique_constraint 应该是一个列表，而不是一个元组。

Answer 2

You are not setting the constraint correctly, it should be like

class UserSite(models.Model):
    user = models.ForeignKey(User, on_delete=models.CASCADE, related_name="sites")
    site = models.ForeignKey(Site, on_delete=models.CASCADE, related_name="users")

    class Meta:
        unique_together = (("user", "site"),)