CODEWITHSUNDEEP
djangodjango-models
Ranu Vijay
Ranu Vijay

Reputation: 1297

Unique together in models

I have a model called Company. In a second model which is Branch, I use Company as a foreign key.

class Branch(models.Model):
    company = models.ForeignKey(Company, on_delete=models.CASCADE)

Now in some other model, I want to set a property(name) unique together with the Company but I use the branch as a foreign key.

class ABC(models.Model):
    name = models.CharField()
    branch = models.ForeignKey(Branch, on_delete=models.CASCADE)

    class Meta:
        unique_together = (
            ('branch__company', 'name'),
        )

Can I do something like the above? It gives me an error that the field is nonexistent. Or can I use both company and branch in my model as foreign key?

class ABC(models.Model):
    name = models.CharField()
    branch = models.ForeignKey(Branch, on_delete=models.CASCADE)
    company = models.ForeignKey(Company, on_delete=models.CASCADE)

    class Meta:
        unique_together = (
            ('company', 'name'),
        )

I want to attach ABC object with a branch but if once added it should be unique to that company (other branches of that company can not have the same name).

Read about the circular error and was thinking of the same here. Unique together will be depreciated in the future but I'm not thinking about this right now.

Any advice?

Upvotes: 0

Views: 199

Answers (1)

Alain Bianchini
Alain Bianchini

Reputation: 4191

I suggest you to perform validation in the clean method (without a database constraint):

from django.core.exceptions import ValidationError


class ABC(models.Model):
    name = models.CharField()
    branch = models.ForeignKey(Branch, on_delete=models.CASCADE)
    
    def clean(self):
       super().clean()
       
       if ABC.objects.filter(name=self.name, branch__company=self.branch.company).exists():
          raise ValidationError('Error message')
 
    def save(self, *args, **kwargs):
       # Forces the clean method to be called
       self.full_clean()
       super().save(*args, **kwargs)

Upvotes: 1

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