so if I have a "company" model and a "person" model, and the "company" model has an owner ( a "person" model instance), and a co-owner( a "person" model instance too), I want to make it so that when the owner is deleted the co-owner becomes the owner and the co-owner becomes empty, is that possible in Django?

CodePudding user response：

Yes it is possible. You could for example override the delete method:

class Company(models.Model):
    owner = models.ForeignKey(
        Person,
        null=True,
        on_delete=models.SET_NULL,
        related_name='owned_companies'
    )

    co_owner = models.ForeignKey(
        Person,
        null=True,
        on_delete=models.SET_NULL,
        related_name='co_owned_companies'
    ) 


class Person(models.Model):
    # fields and stuff...

    def delete(self, *args, **kwargs):
        for company in self.owned_companies.all():
            company.owner = company.co_owner
            company.co_owner = None
            company.save()
        super(Person, self).delete(*args, **kwargs)

Written from mind, maybe on_delete must be models.DO_NOTHING on Company.owner, not sure. But it should generally work.

This won't work with bulk functions. If you want to use djangos bulk functions you need to register a pre delete signal as an alternative method.

CodePudding user response：

What you can do is override the delete method in the Person model so it changes the owner of the Company to the co-owner. Once this change is made it will then delete the Person.

class Company(model.Models):
    owner = models.ForeignKey(Person, null=True, on_delete=DO_NOTHING)
    co_owner = models.ForeignKey(Person, null=True, on_delete=SET_NULL)

class Person(models.Model):
    #Person model stuff here

    def delete(self):
        companies = Company.objects.filter(owner=self)
        
        for company in companies:
            company.owner = company.co_owner
            company.owner = None
            company.save()
            super(Person, self).delete()