xx model inheritance model inheritance exists in two varieties abstract base classes which are a way of specifying common information inherited by the subclasses they don t exist as a separate model nonabstract base classes the default which are models in their own right with their own database tables and everything their subclasses have references back to them created automatically both styles are demonstrated here abstract base classes abstract base classes with related models multitable inheritance an explicit link to the parent we can control the attribute name abstract base classes with related models where the subclass has the same name in a different app and inherits from the same abstract base class note the actual api tests for the following classes are in modelinheritancesamemodelnamemodels py they are defined here in order to have the name conflict between apps ordering used by testinheritedorderingpkdesc abstract base classes abstract base classes with related models multi table inheritance an explicit link to the parent we can control the attribute name abstract base classes with related models where the sub class has the same name in a different app and inherits from the same abstract base class note the actual api tests for the following classes are in model_inheritance_same_model_name models py they are defined here in order to have the name conflict between apps ordering used by test_inherited_ordering_pk_desc
from django.db import models






class CommonInfo(models.Model):
    name = models.CharField(max_length=50)
    age = models.PositiveIntegerField()

    class Meta:
        abstract = True
        ordering = ["name"]

    def __str__(self):
        return "%s %s" % (self.__class__.__name__, self.name)


class Worker(CommonInfo):
    job = models.CharField(max_length=50)


class Student(CommonInfo):
    school_class = models.CharField(max_length=10)

    class Meta:
        pass







class Post(models.Model):
    title = models.CharField(max_length=50)


class Attachment(models.Model):
    post = models.ForeignKey(
        Post,
        models.CASCADE,
        related_name="attached_%(class)s_set",
        related_query_name="attached_%(app_label)s_%(class)ss",
    )
    content = models.TextField()

    class Meta:
        abstract = True


class Comment(Attachment):
    is_spam = models.BooleanField(default=False)


class Link(Attachment):
    url = models.URLField()







class Chef(models.Model):
    name = models.CharField(max_length=50)


class Place(models.Model):
    name = models.CharField(max_length=50)
    address = models.CharField(max_length=80)


class Rating(models.Model):
    rating = models.IntegerField(null=True, blank=True)

    class Meta:
        abstract = True
        ordering = ["-rating"]


class Restaurant(Place, Rating):
    serves_hot_dogs = models.BooleanField(default=False)
    serves_pizza = models.BooleanField(default=False)
    chef = models.ForeignKey(Chef, models.SET_NULL, null=True, blank=True)

    class Meta(Rating.Meta):
        db_table = "my_restaurant"


class ItalianRestaurant(Restaurant):
    serves_gnocchi = models.BooleanField(default=False)


class ItalianRestaurantCommonParent(ItalianRestaurant, Place):
    place_ptr_two = models.OneToOneField(
        Place, on_delete=models.CASCADE, parent_link=True
    )


class Supplier(Place):
    customers = models.ManyToManyField(Restaurant, related_name="provider")


class CustomSupplier(Supplier):
    pass


class ParkingLot(Place):
    
    parent = models.OneToOneField(
        Place, models.CASCADE, primary_key=True, parent_link=True
    )
    main_site = models.ForeignKey(Place, models.CASCADE, related_name="lot")












class Title(models.Model):
    title = models.CharField(max_length=50)


class NamedURL(models.Model):
    title = models.ForeignKey(
        Title, models.CASCADE, related_name="attached_%(app_label)s_%(class)s_set"
    )
    url = models.URLField()

    class Meta:
        abstract = True


class Mixin:
    def __init__(self):
        self.other_attr = 1
        super().__init__()


class MixinModel(models.Model, Mixin):
    pass


class Base(models.Model):
    titles = models.ManyToManyField(Title)


class SubBase(Base):
    sub_id = models.IntegerField(primary_key=True)


class GrandParent(models.Model):
    first_name = models.CharField(max_length=80)
    last_name = models.CharField(max_length=80)
    email = models.EmailField(unique=True)
    place = models.ForeignKey(Place, models.CASCADE, null=True, related_name="+")

    class Meta:
        
        ordering = ["-pk"]
        unique_together = ("first_name", "last_name")


class Parent(GrandParent):
    pass


class Child(Parent):
    pass


class GrandChild(Child):
    pass


class CommonAncestor(models.Model):
    id = models.IntegerField(primary_key=True, default=1)


class FirstParent(CommonAncestor):
    first_ancestor = models.OneToOneField(
        CommonAncestor, models.CASCADE, primary_key=True, parent_link=True
    )


class SecondParent(CommonAncestor):
    second_ancestor = models.OneToOneField(
        CommonAncestor, models.CASCADE, primary_key=True, parent_link=True
    )


class CommonChild(FirstParent, SecondParent):
    pass