CODEWITHSUNDEEP
pythondjangodjango-models
Amistad
Amistad

Reputation: 7400

Allow individual model fields in Django to be null but prevent all of them from being null

i have a Django model class as follows:

class IPGroup(BaseModel):
    """
        Stores IP Groups
    """
    name = models.CharField(max_length=50, unique=True)
    team = models.ForeignKey(Team, on_delete=models.CASCADE)
    _ips = models.ManyToManyField(IP, through='connectivity_service.IPGroupToIP', null=True)
    _cidrs = models.ManyToManyField(CIDR, through='connectivity_service.IPGroupToCIDR', null=True)
    _ip_groups = models.ManyToManyField('self', through='connectivity_service.IPGroupToIPGroup', null=True,
                                        symmetrical=False)

    def __unicode__(self):
        return f'{self.name}'

    class Meta:
        app_label = 'connectivity_service'

As is evident, the fields _ips,_cidrs and ip_groups can be null in the database.However, I want to prevent all 3 of them being null together when the model is saved. In other words, when the model is saved, atleast one of those 3 fields should not be null.

Upvotes: 0

Views: 84

Answers (1)

Daniel Roseman
Daniel Roseman

Reputation: 599470

Firstly, null doesn't have any meaning with a many-to-many field, as that's not actually a column in the database but an entry in a completely separate table.

In any case, if you want to require that at least one of those fields is non-empty, you need to do it at validation time; it's not something you can just specify in the model definition.

But note also, for the same reason as above, you can't do this before creating the model initially; many-to-many fields can't have a value before creation, because they need the ID to create the item in the through table.

Upvotes: 1

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