Re-using set of model fields in Django

问题

My site has two types of users; customers and suppliers. I have ended up with the following class structure:

class Customer(models.Model):
    # stuff specific to customers

class Supplier(models.Model):
    # stuff specific to suppliers

class Profile(models.Model):  # returned by Django's User.get_profile()
    user = models.ForeignKey(User, unique=True)
    customer = models.OneToOneField(Customer, null=True, unique=True)
    supplier = models.OneToOneField(Supplier, null=True, unique=True)

Now I need to add multiple addresses to these models:

both customers and suppliers should have their "user" address, so should be in Profile
customers also have a billing address, should be in Customer then

Address would be something like:

class Address(models.Model):
    street1 = models.CharField(max_length=100)
    street2 = models.CharField(max_length=100)
    zipcode = models.CharField(max_length=16)
    city = models.CharField(max_length=100)
    state = models.CharField(max_length=100)
    country = models.CharField(max_length=100)

I can see two straightforward solutions to re-use the address information: either refer to Address via ForeignKey from Profile & Customer classes, or inherit Profile & Customer classes from Address.

I can see some pros for both approaches:

ForeignKey

groups the address data nicely behind one field instead of "polluting" the model
no risk of multiple inheritance in future

Inheritance

easier access to fields
fewer database joins
addresses are automatically visible with the object in Django's admin

Which one would you go with and why? Do you think either of the solutions is inherently bad? Do you see some better alternatives?

回答1:

I would probably go with the Foreign Key approach - I think it's cleaner.

Dealing with the "pros" of inheritance you list:

It's easy to access fields belonging to an object that is Foreign Keyed - my_customer.address.zipcode isn't too hard, is it?
I doubt you'll find joins prohibitively expensive, and if you do you can always avoid them when fetching lots of Customers/Suppliers.
You can always display addresses alongside the object in Django's admin if you define a __unicode__() method on Address, and just add address (if that's what you call the ForeignKey property of Customer) to your admin's list_display.

来源：https://stackoverflow.com/questions/3933997/re-using-set-of-model-fields-in-django

标签

django

django-models

code-reuse