170 lines
4.2 KiB
Python
170 lines
4.2 KiB
Python
"""
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By specifying the 'proxy' Meta attribute, model subclasses can specify that
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they will take data directly from the table of their base class table rather
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than using a new table of their own. This allows them to act as simple proxies,
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providing a modified interface to the data from the base class.
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"""
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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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# A couple of managers for testing managing overriding in proxy model cases.
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class PersonManager(models.Manager):
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def get_queryset(self):
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return super(PersonManager, self).get_queryset().exclude(name="fred")
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class SubManager(models.Manager):
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def get_queryset(self):
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return super(SubManager, self).get_queryset().exclude(name="wilma")
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@python_2_unicode_compatible
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class Person(models.Model):
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"""
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A simple concrete base class.
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"""
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name = models.CharField(max_length=50)
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objects = PersonManager()
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def __str__(self):
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return self.name
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class Abstract(models.Model):
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"""
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A simple abstract base class, to be used for error checking.
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"""
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data = models.CharField(max_length=10)
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class Meta:
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abstract = True
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class MyPerson(Person):
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"""
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A proxy subclass, this should not get a new table. Overrides the default
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manager.
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"""
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class Meta:
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proxy = True
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ordering = ["name"]
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permissions = (
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("display_users", "May display users information"),
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)
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objects = SubManager()
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other = PersonManager()
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def has_special_name(self):
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return self.name.lower() == "special"
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class ManagerMixin(models.Model):
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excluder = SubManager()
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class Meta:
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abstract = True
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class OtherPerson(Person, ManagerMixin):
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"""
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A class with the default manager from Person, plus an secondary manager.
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"""
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class Meta:
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proxy = True
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ordering = ["name"]
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class StatusPerson(MyPerson):
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"""
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A non-proxy subclass of a proxy, it should get a new table.
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"""
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status = models.CharField(max_length=80)
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# We can even have proxies of proxies (and subclass of those).
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class MyPersonProxy(MyPerson):
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class Meta:
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proxy = True
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class LowerStatusPerson(MyPersonProxy):
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status = models.CharField(max_length=80)
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@python_2_unicode_compatible
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class User(models.Model):
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name = models.CharField(max_length=100)
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def __str__(self):
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return self.name
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class UserProxy(User):
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class Meta:
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proxy = True
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class UserProxyProxy(UserProxy):
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class Meta:
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proxy = True
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# We can still use `select_related()` to include related models in our querysets.
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class Country(models.Model):
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name = models.CharField(max_length=50)
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@python_2_unicode_compatible
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class State(models.Model):
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name = models.CharField(max_length=50)
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country = models.ForeignKey(Country)
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def __str__(self):
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return self.name
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class StateProxy(State):
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class Meta:
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proxy = True
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# Proxy models still works with filters (on related fields)
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# and select_related, even when mixed with model inheritance
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class BaseUser(models.Model):
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name = models.CharField(max_length=255)
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class TrackerUser(BaseUser):
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status = models.CharField(max_length=50)
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class ProxyTrackerUser(TrackerUser):
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class Meta:
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proxy = True
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@python_2_unicode_compatible
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class Issue(models.Model):
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summary = models.CharField(max_length=255)
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assignee = models.ForeignKey(TrackerUser)
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def __str__(self):
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return ':'.join((self.__class__.__name__,self.summary,))
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class Bug(Issue):
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version = models.CharField(max_length=50)
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reporter = models.ForeignKey(BaseUser)
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class ProxyBug(Bug):
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"""
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Proxy of an inherited class
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"""
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class Meta:
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proxy = True
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class ProxyProxyBug(ProxyBug):
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"""
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A proxy of proxy model with related field
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"""
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class Meta:
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proxy = True
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class Improvement(Issue):
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"""
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A model that has relation to a proxy model
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or to a proxy of proxy model
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"""
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version = models.CharField(max_length=50)
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reporter = models.ForeignKey(ProxyTrackerUser)
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associated_bug = models.ForeignKey(ProxyProxyBug)
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class ProxyImprovement(Improvement):
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class Meta:
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proxy = True
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