Django models dependencies and transfer ownership - django

Question

What I am trying to build is a app that can deal with honey production management.
There are number of producers that produce honey pots and they can give their pots to a variety of stores that have their customers. One producer can give his production to many stores, and a store can have honey pots from many producers. Honey pots can be tracked by pot_id. The models.py looks like this:
class Produser(models.Model):
name = models.CharField(max_length=255)
address = models.CharField(max_length=255)
class Store(models.Model):
name = models.CharField(max_length=255)
address = models.CharField(max_length=255)
produser= models.ManyToManyField(Produser)
class Customer(models.Model):
first_name = models.CharField(max_length=255)
last_name = models.CharField(max_length=255)
store = = models.ForeignKey(Store, on_delete=models.CASCADE)
class HoneyPot(models.Model):
produced_date = models.DateField(auto_now=False)
pot_id = models.CharField(max_length=25, blank=False)
produser= models.ForeignKey(Produser, on_delete=models.CASCADE)
store= models.ForeignKey(Store, on_delete=models.CASCADE)
customer = models.ForeignKey(Customer, on_delete=models.CASCADE)
I'm struggling to find how to modify the models in the way that one pot to be owned or by producer or a shop or a customer. As right now when a new pot is created store and customers are required fields.

Answer 1

You can say that Produser, Store and Customer all have something in common, i.e. they can own a HoneyPot. Meaning they are specializations of let's say an entity that can own a HoneyPot. To model this we would simply add an extra model which Produser, Store and Customer all will either inherit from or have a one to one relationship with.
Using a OneToOneField [Django docs]:
We can simply make the relationship by using a OneToOneField:
class HoneyPotOwner(models.Model):
PRODUCER = 'P'
STORE = 'S'
CONSUMER = 'C'
TYPE_CHOICES = [
(PRODUCER, 'Producer'),
(STORE, 'Store'),
(CONSUMER, 'Consumer'),
]
owner_type = models.CharField(max_length=1, choices=TYPE_CHOICES)
class Produser(models.Model):
honey_pot_owner = models.OneToOneField(HoneyPotOwner, on_delete=models.CASCADE)
...
class Store(models.Model):
honey_pot_owner = models.OneToOneField(HoneyPotOwner, on_delete=models.CASCADE)
...
class Customer(models.Model):
honey_pot_owner = models.OneToOneField(HoneyPotOwner, on_delete=models.CASCADE)
...
class HoneyPot(models.Model):
produced_date = models.DateField(auto_now=False)
pot_id = models.CharField(max_length=25, blank=False)
owner = models.ForeignKey(HoneyPotOwner, on_delete=models.CASCADE)
Using Multi-table inheritance:
We can have Produser, Store and Customer inherit from HoneyPotOwner this is called Multi-table inheritance. This implicitly makes the OneToOneField, but has a few advantage that accessing the related fields becomes a little easier:
class HoneyPotOwner(models.Model):
PRODUCER = 'P'
STORE = 'S'
CONSUMER = 'C'
TYPE_CHOICES = [
(PRODUCER, 'Producer'),
(STORE, 'Store'),
(CONSUMER, 'Consumer'),
]
owner_type = models.CharField(max_length=1, choices=TYPE_CHOICES)
class Produser(HoneyPotOwner):
...
class Store(HoneyPotOwner):
...
class Customer(HoneyPotOwner):
...
class HoneyPot(models.Model):
produced_date = models.DateField(auto_now=False)
pot_id = models.CharField(max_length=25, blank=False)
owner = models.ForeignKey(HoneyPotOwner, on_delete=models.CASCADE)