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"""
By specifying the 'proxy' Meta attribute, model subclasses can specify that
they will take data directly from the table of their base class table rather
than using a new table of their own. This allows them to act as simple proxies,
providing a modified interface to the data from the base class.
"""
from django.db import models
# A couple of managers for testing managing overriding in proxy model cases.
class PersonManager(models.Manager):
def get_query_set(self):
return super(PersonManager, self).get_query_set().exclude(name="fred")
class SubManager(models.Manager):
def get_query_set(self):
return super(SubManager, self).get_query_set().exclude(name="wilma")
class Person(models.Model):
"""
A simple concrete base class.
"""
name = models.CharField(max_length=50)
objects = PersonManager()
def __unicode__(self):
return self.name
class Abstract(models.Model):
"""
A simple abstract base class, to be used for error checking.
"""
data = models.CharField(max_length=10)
class Meta:
abstract = True
class MyPerson(Person):
"""
A proxy subclass, this should not get a new table. Overrides the default
manager.
"""
class Meta:
proxy = True
ordering = ["name"]
objects = SubManager()
other = PersonManager()
def has_special_name(self):
return self.name.lower() == "special"
class ManagerMixin(models.Model):
excluder = SubManager()
class Meta:
abstract = True
class OtherPerson(Person, ManagerMixin):
"""
A class with the default manager from Person, plus an secondary manager.
"""
class Meta:
proxy = True
ordering = ["name"]
class StatusPerson(MyPerson):
"""
A non-proxy subclass of a proxy, it should get a new table.
"""
status = models.CharField(max_length=80)
# We can even have proxies of proxies (and subclass of those).
class MyPersonProxy(MyPerson):
class Meta:
proxy = True
class LowerStatusPerson(MyPersonProxy):
status = models.CharField(max_length=80)
__test__ = {'API_TESTS' : """
# The MyPerson model should be generating the same database queries as the
# Person model (when the same manager is used in each case).
>>> MyPerson.other.all().query.as_sql() == Person.objects.order_by("name").query.as_sql()
True
# The StatusPerson models should have its own table (it's using ORM-level
# inheritance).
>>> StatusPerson.objects.all().query.as_sql() == Person.objects.all().query.as_sql()
False
# Creating a Person makes them accessible through the MyPerson proxy.
>>> _ = Person.objects.create(name="Foo McBar")
>>> len(Person.objects.all())
1
>>> len(MyPerson.objects.all())
1
>>> MyPerson.objects.get(name="Foo McBar").id
1
>>> MyPerson.objects.get(id=1).has_special_name()
False
# Person is not proxied by StatusPerson subclass, however.
>>> StatusPerson.objects.all()
[]
# A new MyPerson also shows up as a standard Person
>>> _ = MyPerson.objects.create(name="Bazza del Frob")
>>> len(MyPerson.objects.all())
2
>>> len(Person.objects.all())
2
>>> _ = LowerStatusPerson.objects.create(status="low", name="homer")
>>> LowerStatusPerson.objects.all()
[<LowerStatusPerson: homer>]
# And now for some things that shouldn't work...
#
# All base classes must be non-abstract
>>> class NoAbstract(Abstract):
... class Meta:
... proxy = True
Traceback (most recent call last):
....
TypeError: Abstract base class containing model fields not permitted for proxy model 'NoAbstract'.
# The proxy must actually have one concrete base class
>>> class TooManyBases(Person, Abstract):
... class Meta:
... proxy = True
Traceback (most recent call last):
....
TypeError: Abstract base class containing model fields not permitted for proxy model 'TooManyBases'.
>>> class NoBaseClasses(models.Model):
... class Meta:
... proxy = True
Traceback (most recent call last):
....
TypeError: Proxy model 'NoBaseClasses' has no non-abstract model base class.
# A proxy cannot introduce any new fields
>>> class NoNewFields(Person):
... newfield = models.BooleanField()
... class Meta:
... proxy = True
Traceback (most recent call last):
....
FieldError: Proxy model 'NoNewFields' contains model fields.
# Manager tests.
>>> Person.objects.all().delete()
>>> _ = Person.objects.create(name="fred")
>>> _ = Person.objects.create(name="wilma")
>>> _ = Person.objects.create(name="barney")
>>> MyPerson.objects.all()
[<MyPerson: barney>, <MyPerson: fred>]
>>> MyPerson._default_manager.all()
[<MyPerson: barney>, <MyPerson: fred>]
>>> OtherPerson.objects.all()
[<OtherPerson: barney>, <OtherPerson: wilma>]
>>> OtherPerson.excluder.all()
[<OtherPerson: barney>, <OtherPerson: fred>]
>>> OtherPerson._default_manager.all()
[<OtherPerson: barney>, <OtherPerson: wilma>]
"""}
|
