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"""
23. Giving models a custom manager
You can use a custom ``Manager`` in a particular model by extending the base
``Manager`` class and instantiating your custom ``Manager`` in your model.
There are two reasons you might want to customize a ``Manager``: to add extra
``Manager`` methods, and/or to modify the initial ``QuerySet`` the ``Manager``
returns.
"""
from __future__ import unicode_literals
from django.contrib.contenttypes.fields import (
GenericForeignKey, GenericRelation
)
from django.db import models
from django.utils.encoding import python_2_unicode_compatible
# An example of a custom manager called "objects".
class PersonManager(models.Manager):
def get_fun_people(self):
return self.filter(fun=True)
# An example of a custom manager that sets get_queryset().
class PublishedBookManager(models.Manager):
def get_queryset(self):
return super(PublishedBookManager, self).get_queryset().filter(is_published=True)
# An example of a custom queryset that copies its methods onto the manager.
class CustomQuerySet(models.QuerySet):
def filter(self, *args, **kwargs):
queryset = super(CustomQuerySet, self).filter(fun=True)
queryset._filter_CustomQuerySet = True
return queryset
def public_method(self, *args, **kwargs):
return self.all()
def _private_method(self, *args, **kwargs):
return self.all()
def optout_public_method(self, *args, **kwargs):
return self.all()
optout_public_method.queryset_only = True
def _optin_private_method(self, *args, **kwargs):
return self.all()
_optin_private_method.queryset_only = False
class BaseCustomManager(models.Manager):
def __init__(self, arg):
super(BaseCustomManager, self).__init__()
self.init_arg = arg
def filter(self, *args, **kwargs):
queryset = super(BaseCustomManager, self).filter(fun=True)
queryset._filter_CustomManager = True
return queryset
def manager_only(self):
return self.all()
CustomManager = BaseCustomManager.from_queryset(CustomQuerySet)
class FunPeopleManager(models.Manager):
def get_queryset(self):
return super(FunPeopleManager, self).get_queryset().filter(fun=True)
class BoringPeopleManager(models.Manager):
def get_queryset(self):
return super(BoringPeopleManager, self).get_queryset().filter(fun=False)
@python_2_unicode_compatible
class Person(models.Model):
first_name = models.CharField(max_length=30)
last_name = models.CharField(max_length=30)
fun = models.BooleanField(default=False)
favorite_book = models.ForeignKey('Book', null=True, related_name='favorite_books')
favorite_thing_type = models.ForeignKey('contenttypes.ContentType', null=True)
favorite_thing_id = models.IntegerField(null=True)
favorite_thing = GenericForeignKey('favorite_thing_type', 'favorite_thing_id')
objects = PersonManager()
fun_people = FunPeopleManager()
boring_people = BoringPeopleManager()
custom_queryset_default_manager = CustomQuerySet.as_manager()
custom_queryset_custom_manager = CustomManager('hello')
def __str__(self):
return "%s %s" % (self.first_name, self.last_name)
@python_2_unicode_compatible
class FunPerson(models.Model):
first_name = models.CharField(max_length=30)
last_name = models.CharField(max_length=30)
fun = models.BooleanField(default=True)
favorite_book = models.ForeignKey('Book', null=True, related_name='fun_people_favorite_books')
favorite_thing_type = models.ForeignKey('contenttypes.ContentType', null=True)
favorite_thing_id = models.IntegerField(null=True)
favorite_thing = GenericForeignKey('favorite_thing_type', 'favorite_thing_id')
objects = FunPeopleManager()
def __str__(self):
return "%s %s" % (self.first_name, self.last_name)
@python_2_unicode_compatible
class Book(models.Model):
title = models.CharField(max_length=50)
author = models.CharField(max_length=30)
is_published = models.BooleanField(default=False)
published_objects = PublishedBookManager()
authors = models.ManyToManyField(Person, related_name='books')
fun_authors = models.ManyToManyField(FunPerson, related_name='books')
favorite_things = GenericRelation(Person,
content_type_field='favorite_thing_type', object_id_field='favorite_thing_id')
fun_people_favorite_things = GenericRelation(FunPerson,
content_type_field='favorite_thing_type', object_id_field='favorite_thing_id')
def __str__(self):
return self.title
# An example of providing multiple custom managers.
class FastCarManager(models.Manager):
def get_queryset(self):
return super(FastCarManager, self).get_queryset().filter(top_speed__gt=150)
@python_2_unicode_compatible
class Car(models.Model):
name = models.CharField(max_length=10)
mileage = models.IntegerField()
top_speed = models.IntegerField(help_text="In miles per hour.")
cars = models.Manager()
fast_cars = FastCarManager()
def __str__(self):
return self.name
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