1 """

     2 23. Giving models a custom manager

     3 

     4 You 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 

     7 There 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``

     9 returns.

    10 """

    11 

    12 from django.db import models

    13 

    14 # An example of a custom manager called "objects".

    15 

    16 class PersonManager(models.Manager):

    17     def get_fun_people(self):

    18         return self.filter(fun=True)

    19 

    20 class 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 

    31 class PublishedBookManager(models.Manager):

    32     def get_query_set(self):

    33         return super(PublishedBookManager, self).get_query_set().filter(is_published=True)

    34 

    35 class 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 

    47 class FastCarManager(models.Manager):

    48     def get_query_set(self):

    49         return super(FastCarManager, self).get_query_set().filter(top_speed__gt=150)

    50 

    51 class 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