django multiple models with same foreign key

Question

I have django app that is tracking contracts, locations, and products for various clients. Contracts, Locations each reference the client with a ForeignKey.

class Location(models.Model):
    client = models.ForeignKey(Client, on_delete=models.CASCADE)
    ...

class Contract(models.Model):
    client = models.ForeignKey(Client, on_delete=models.CASCADE)
    ...

I also have a product that will be deployed in a location, on a contract, for a client. I need to include client in product because the reference is used to secure the record to that client.

class Product(models.Model):
    client = models.ForeignKey(Client, on_delete=models.CASCADE)
    contract = models.ForeignKey(Contract, on_delete=models.CASCADE)
    location = models.ForeignKey(Location, on_delete=models.CASCADE)
    ....

What is the best way to make sure a product is never created that contains a different client reference across all 3 models? I was thinking I could use a pre_save signal but I would rather use a database constraint but I don't see a database constraint to force this.

Answer 1

Did you look into the unique_together. I think this will do what you want to do.

Also keep the following in mind.

UniqueConstraint provides more functionality than unique_together. unique_together may be deprecated in the future.