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