django charge users based on how many counties they want to access - django

Question

I'm building a web app,
basically I currently have 3 models ,
1- State: which represents all US states
2- County: which represents all counties with foreign key of state
3- Home: which represents all homes with foreign key of County
the app will show homes,
but users needs to subscribe for certain counties (the counties prices can vary)
the goal is : when users subscribe to certain counties they can see the related "Homes" to these counties
I'm not sure how should I represent these relations between users, subscriptions and how to connect it to County model I have.
and how to make a view for the user to add new counties.
Thank you.
Update (My models):
class State(models.Model):
state_name = models.CharField(max_length=50)
def __str__(self):
return self.state_name
class County(models.Model):
county_name = models.CharField(max_length=50)
state = models.ForeignKey(State, on_delete=models.CASCADE)
def __str__(self):
return self.county_name
class Meta:
unique_together = ("county_name", "state")
verbose_name_plural = 'Counties'
class Home(models.Model):
owner_name = models.CharField(max_length=100, null=True, blank=True)
street_address = models.CharField(max_length=100, null=True, blank=True)
city = models.CharField(max_length=50, null=True, blank=True)
county = models.ForeignKey(County, on_delete=models.CASCADE)
postal_code = models.CharField(max_length=50, null=True, blank=True)
price = models.CharField(max_length=50, null=True, blank=True)
sqft = models.CharField(max_length=50, null=True, blank=True)
home_type = models.CharField(max_length=100, null=True, blank=True)
geom = models.PointField()
added = models.DateTimeField(auto_now_add=True)
updated = models.DateTimeField(auto_now=True)
def __str__(self):
return '{}, {}, {}'.format(self.street_address, self.city, self.county.state.state_name)
class Meta:
verbose_name = 'Home'
verbose_name_plural = 'Homes'
#property
def state_county(self):
return f'{self.county.county_name}_{self.state}'
#property
def state(self):
return self.county.state.state_name

Answer 1

Here is a basic idea, you should evaluate from this point.
class State(models.Model)
name = models.CharField(max_length=100)
class County(models.Model)
state = models.ForeignKey(State)
name = models.CharField(max_length=100)
class Home(models.Model)
county= models.ForeignKey(County)
name = models.CharField(max_length=100)
class Subscription(models.Model)
county = models.ForeignKey(County)
user = models.ForeignKey(User)
Basically, you can then charge your user per County (observe that one can have more than one County subscription)
Another aproach would be to use a hierarchy to have State>County>Home, on a MPTT, but maybe its not what you want.

Answer 2

One way would be to add ManyToMany County relationship field in the Subscriptions model and then you would query subscribed county and filter Home.
Something in the sense of:
class County(models.Model):
county = models.CharField(max_length=255)
class Home(models.Model):
county = models.ForeignKey(County, on_delete=models.PROTECT)
class Subscription(models.Model):
user = models.ForeingKey(User, on_delete=models.PROTECT)
county = models.ManyToMany(County)
Then you'd query subscriptions and filter based on that.
subscriptions = Subscription.objects.filter(user=request.user).values_list('county', flat=True)
homes = Home.objects.filter(county_id__in=subscriptions)
You could further improved that with models Manager on Subscription to avoid filtering user every time with something like:
class SubscriptionManager(models.Manager):
def user_subscriptions(self, user):
return super().get_queryset().filter(user=user)
class Subscription(models.Model):
user = models.ForeingKey(User, on_delete=models.PROTECT)
county = models.ManyToMany(County)
objects = SubscriptionManager()
and then filter either with:
subscriptions = Subscription.objects.filter(user=request.user).values_list('county', flat=True)
or
subscriptions = Subscription.objects.user_subscriptions(request.user).values_list('county', flat=True)