Question

我的模型如下所示：

class LibraryEntry(models.Model):
  host_lib_song_id = models.IntegerField()
  song = models.CharField(max_length=200)
  artist = models.CharField(max_length=200)
  album = models.CharField(max_length=200)
  owning_user = models.ForeignKey(User)
  is_deleted = models.BooleanField(default=False)

现在，如果我选择is_deleted=False，那么host_lib_song_id和owning_user的组合应该是唯一的。我怎么能表达这个呢？

Answer 1

如果is_deleted为False更合适，请覆盖validate_unique以检查唯一性：

...

def validate_unique(self, exclude=None):
    if not self.is_deleted and \
       LibraryEntry.objects.exclude(pk=self.pk).filter(host_lib_song_id=self.host_lib_song_id, owning_user=self.owning_user).exists():
        raise ValidationError('Some error message about uniqueness required')
    super(LibraryEntry, self).validate_unique(exclude=exclude)

Answer 2

您不能通过Meta.unique_together约束来表达这一点，而是通过django's model validation：

class LibraryEntry(models.Model):
    def clean(self):
        from django.core.exceptions import ValidationError
        try:
            # try to find a duplicate entry and exclude 'self'
            duplicate = LibraryEntry.objects.exclude(pk=self.pk)\
                .get(owning_user=self.owning_user, 
                     host_lib_song_id=self.host_lib_song_id,
                     is_deleted=False)
            raise ValidationError('Library Entry already exists!')
        except: LibraryEntry.DoesNotExist:
            # no duplicate found
            pass

Answer 3

如果您使用的是Django 2.2及更高版本，则可以使用UniqueConstraint。您可以看到完整的答案here。

Django条件独特在一起

3 个答案: