django/tests/model_inheritance/models.py

"""
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.
    - non-abstract 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.
"""
from django.db import models


#
# Abstract base classes
#


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


#
# Abstract base classes with related models
#

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

    def __str__(self):
        return self.content


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


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


#
# Multi-table inheritance
#

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

    def __str__(self):
        return "%s the chef" % self.name


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

    def __str__(self):
        return "%s the place" % self.name


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'

    def __str__(self):
        return "%s the restaurant" % self.name


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

    def __str__(self):
        return "%s the italian restaurant" % self.name


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

    def __str__(self):
        return "%s the supplier" % self.name


class ParkingLot(Place):
    # An explicit link to the parent (we can control the attribute name).
    parent = models.OneToOneField(Place, models.CASCADE, primary_key=True, parent_link=True)
    main_site = models.ForeignKey(Place, models.CASCADE, related_name='lot')

    def __str__(self):
        return "%s the parking lot" % self.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
#

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)

    class Meta:
        unique_together = ('first_name', 'last_name')


class Parent(GrandParent):
    pass


class Child(Parent):
    pass


class GrandChild(Child):
    pass