/tests/modeltests/custom_managers/models.py

 1"""
 223. Giving models a custom manager
 3
 4You can use a custom ``Manager`` in a particular model by extending the base
 5``Manager`` class and instantiating your custom ``Manager`` in your model.
 6
 7There are two reasons you might want to customize a ``Manager``: to add extra
 8``Manager`` methods, and/or to modify the initial ``QuerySet`` the ``Manager``
 9returns.
10"""
11
12from django.db import models
13
14# An example of a custom manager called "objects".
15
16class PersonManager(models.Manager):
17    def get_fun_people(self):
18        return self.filter(fun=True)
19
20class Person(models.Model):
21    first_name = models.CharField(max_length=30)
22    last_name = models.CharField(max_length=30)
23    fun = models.BooleanField()
24    objects = PersonManager()
25
26    def __unicode__(self):
27        return u"%s %s" % (self.first_name, self.last_name)
28
29# An example of a custom manager that sets get_query_set().
30
31class PublishedBookManager(models.Manager):
32    def get_query_set(self):
33        return super(PublishedBookManager, self).get_query_set().filter(is_published=True)
34
35class Book(models.Model):
36    title = models.CharField(max_length=50)
37    author = models.CharField(max_length=30)
38    is_published = models.BooleanField()
39    published_objects = PublishedBookManager()
40    authors = models.ManyToManyField(Person, related_name='books')
41
42    def __unicode__(self):
43        return self.title
44
45# An example of providing multiple custom managers.
46
47class FastCarManager(models.Manager):
48    def get_query_set(self):
49        return super(FastCarManager, self).get_query_set().filter(top_speed__gt=150)
50
51class Car(models.Model):
52    name = models.CharField(max_length=10)
53    mileage = models.IntegerField()
54    top_speed = models.IntegerField(help_text="In miles per hour.")
55    cars = models.Manager()
56    fast_cars = FastCarManager()
57
58    def __unicode__(self):
59        return self.name