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"""
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 __unicode__(self):
return u'%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 StudentWorker(Student, Worker):
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, related_name='attached_%(class)s_set')
content = models.TextField()
class Meta:
abstract = True
def __unicode__(self):
return self.content
class Comment(Attachment):
is_spam = models.BooleanField()
class Link(Attachment):
url = models.URLField()
#
# Multi-table inheritance
#
class Chef(models.Model):
name = models.CharField(max_length=50)
def __unicode__(self):
return u"%s the chef" % self.name
class Place(models.Model):
name = models.CharField(max_length=50)
address = models.CharField(max_length=80)
def __unicode__(self):
return u"%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()
serves_pizza = models.BooleanField()
chef = models.ForeignKey(Chef, null=True, blank=True)
class Meta(Rating.Meta):
db_table = 'my_restaurant'
def __unicode__(self):
return u"%s the restaurant" % self.name
class ItalianRestaurant(Restaurant):
serves_gnocchi = models.BooleanField()
def __unicode__(self):
return u"%s the italian restaurant" % self.name
class Supplier(Place):
customers = models.ManyToManyField(Restaurant, related_name='provider')
def __unicode__(self):
return u"%s the supplier" % self.name
class ParkingLot(Place):
# An explicit link to the parent (we can control the attribute name).
parent = models.OneToOneField(Place, primary_key=True, parent_link=True)
main_site = models.ForeignKey(Place, related_name='lot')
def __unicode__(self):
return u"%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, related_name='attached_%(app_label)s_%(class)s_set')
url = models.URLField()
class Meta:
abstract = True
class Copy(NamedURL):
content = models.TextField()
def __unicode__(self):
return self.content
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