queryset-refactor: Model inheritance support.

This adds both types of model inheritance: abstract base classes (ABCs) and
multi-table inheritance. See the documentation and tests / examples for details.

Still a few known bugs here, so don't file tickets (I know about them). Not
quite ready for prime-time usage, but it mostly works as expected.


git-svn-id: http://code.djangoproject.com/svn/django/branches/queryset-refactor@7126 bcc190cf-cafb-0310-a4f2-bffc1f526a37

1 files changed, 146 insertions, 11 deletions

diff --git a/tests/modeltests/model_inheritance/models.py b/tests/modeltests/model_inheritance/models.py
index d9956a5452..940b2ee10c 100644
--- a/tests/modeltests/model_inheritance/models.py
+++ b/tests/modeltests/model_inheritance/models.py
@@ -1,11 +1,35 @@
 """
 XX. Model inheritance
 
-Model inheritance isn't yet supported.
+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
 
+class CommonInfo(models.Model):
+    name = models.CharField(max_length=50)
+    age = models.PositiveIntegerField()
+
+    class Meta:
+        abstract = True
+
+    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 Place(models.Model):
     name = models.CharField(max_length=50)
     address = models.CharField(max_length=80)
@@ -26,16 +50,44 @@ class ItalianRestaurant(Restaurant):
     def __unicode__(self):
         return u"%s the italian restaurant" % self.name
 
-# XFAIL: Recent changes to model saving mean these now fail catastrophically.
-# They'll be re-enabled when the porting is a bit further along.
-not__test__ = {'API_TESTS':"""
-# Make sure Restaurant has the right fields in the right order.
->>> [f.name for f in Restaurant._meta.fields]
-['id', 'name', 'address', 'serves_hot_dogs', 'serves_pizza']
+class Supplier(Place):
+    customers = models.ManyToManyField(Restaurant, related_name='provider')
 
-# Make sure ItalianRestaurant has the right fields in the right order.
->>> [f.name for f in ItalianRestaurant._meta.fields]
-['id', 'name', 'address', 'serves_hot_dogs', 'serves_pizza', 'serves_gnocchi']
+    def __unicode__(self):
+        return u"%s the supplier" % self.name
+
+class ParkingLot(Place):
+    main_site = models.ForeignKey(Place, related_name='lot')
+
+    def __unicode__(self):
+        return u"%s the parking lot" % self.name
+
+__test__ = {'API_TESTS':"""
+# The Student and Worker models both have 'name' and 'age' fields on them and
+# inherit the __unicode__() method, just as with normal Python subclassing.
+# This is useful if you want to factor out common information for programming
+# purposes, but still completely independent separate models at the database
+# level.
+
+>>> w = Worker(name='Fred', age=35, job='Quarry worker')
+>>> w.save()
+>>> s = Student(name='Pebbles', age=5, school_class='1B')
+>>> s.save()
+>>> unicode(w)
+u'Worker Fred'
+>>> unicode(s)
+u'Student Pebbles'
+
+# However, the CommonInfo class cannot be used as a normal model (it doesn't
+# exist as a model).
+>>> CommonInfo.objects.all()
+Traceback (most recent call last):
+    ...
+AttributeError: type object 'CommonInfo' has no attribute 'objects'
+
+# The Place/Restaurant/ItalianRestaurant models, on the other hand, all exist
+# as independent models. However, the subclasses also have transparent access
+# to the fields of their ancestors.
 
 # Create a couple of Places.
 >>> p1 = Place(name='Master Shakes', address='666 W. Jersey')
@@ -43,7 +95,7 @@ not__test__ = {'API_TESTS':"""
 >>> p2 = Place(name='Ace Hardware', address='1013 N. Ashland')
 >>> p2.save()
 
-# Test constructor for Restaurant.
+Test constructor for Restaurant.
 >>> r = Restaurant(name='Demon Dogs', address='944 W. Fullerton', serves_hot_dogs=True, serves_pizza=False)
 >>> r.save()
 
@@ -51,5 +103,88 @@ not__test__ = {'API_TESTS':"""
 >>> ir = ItalianRestaurant(name='Ristorante Miron', address='1234 W. Elm', serves_hot_dogs=False, serves_pizza=False, serves_gnocchi=True)
 >>> ir.save()
 
+# Make sure Restaurant and ItalianRestaurant have the right fields in the right
+# order.
+>>> [f.name for f in Restaurant._meta.fields]
+['id', 'name', 'address', 'place_ptr', 'serves_hot_dogs', 'serves_pizza']
+>>> [f.name for f in ItalianRestaurant._meta.fields]
+['id', 'name', 'address', 'place_ptr', 'serves_hot_dogs', 'serves_pizza', 'restaurant_ptr', 'serves_gnocchi']
+
+# Even though p.supplier for a Place 'p' (a parent of a Supplier), a Restaurant
+# object cannot access that reverse relation, since it's not part of the
+# Place-Supplier Hierarchy.
+>>> Place.objects.filter(supplier__name='foo')
+[]
+>>> Restaurant.objects.filter(supplier__name='foo')
+Traceback (most recent call last):
+    ...
+TypeError: Cannot resolve keyword 'supplier' into field. Choices are: address, id, italianrestaurant, lot, name, place_ptr, provider, serves_hot_dogs, serves_pizza
+
+# Parent fields can be used directly in filters on the child model.
+>>> Restaurant.objects.filter(name='Demon Dogs')
+[<Restaurant: Demon Dogs the restaurant>]
+>>> ItalianRestaurant.objects.filter(address='1234 W. Elm')
+[<ItalianRestaurant: Ristorante Miron the italian restaurant>]
+
+# Filters against the parent model return objects of the parent's type.
+>>> Place.objects.filter(name='Demon Dogs')
+[<Place: Demon Dogs the place>]
+
+# Since the parent and child are linked by an automatically created
+# OneToOneField, you can get from the parent to the child by using the child's
+# name.
+>>> place = Place.objects.get(name='Demon Dogs')
+>>> place.restaurant
+<Restaurant: Demon Dogs the restaurant>
+
+>>> Place.objects.get(name='Ristorante Miron').restaurant.italianrestaurant
+<ItalianRestaurant: Ristorante Miron the italian restaurant>
+>>> Restaurant.objects.get(name='Ristorante Miron').italianrestaurant
+<ItalianRestaurant: Ristorante Miron the italian restaurant>
+
+# This won't work because the Demon Dogs restaurant is not an Italian
+# restaurant.
+>>> place.restaurant.italianrestaurant
+Traceback (most recent call last):
+    ...
+DoesNotExist: ItalianRestaurant matching query does not exist.
+
+# Related objects work just as they normally do.
+
+>>> s1 = Supplier(name="Joe's Chickens", address='123 Sesame St')
+>>> s1.save()
+>>> s1.customers = [r, ir]
+>>> s2 = Supplier(name="Luigi's Pasta", address='456 Sesame St')
+>>> s2.save()
+>>> s2.customers = [ir]
+
+# This won't work because the Place we select is not a Restaurant (it's a
+# Supplier).
+>>> p = Place.objects.get(name="Joe's Chickens")
+>>> p.restaurant
+Traceback (most recent call last):
+    ...
+DoesNotExist: Restaurant matching query does not exist.
+
+# But we can descend from p to the Supplier child, as expected.
+>>> p.supplier
+<Supplier: Joe's Chickens the supplier>
+
+>>> ir.provider.order_by('-name')
+[<Supplier: Luigi's Pasta the supplier>, <Supplier: Joe's Chickens the supplier>]
+
+>>> Restaurant.objects.filter(provider__name__contains="Chickens")
+[<Restaurant: Demon Dogs the restaurant>, <Restaurant: Ristorante Miron the restaurant>]
+>>> ItalianRestaurant.objects.filter(provider__name__contains="Chickens")
+[<ItalianRestaurant: Ristorante Miron the italian restaurant>]
+
+>>> park1 = ParkingLot(name='Main St', address='111 Main St', main_site=s1)
+>>> park1.save()
+>>> park2 = ParkingLot(name='Well Lit', address='124 Sesame St', main_site=ir)
+>>> park2.save()
+
+>>> Restaurant.objects.get(lot__name='Well Lit')
+<Restaurant: Ristorante Miron the restaurant>
+
 
 """}