mirror of
https://github.com/django/django.git
synced 2024-12-23 09:36:06 +00:00
b065aeb17f
Cleaned up the internal implementation of m2m fields by removing related.py _get_fk_val(). The _get_fk_val() was doing the wrong thing if asked for the foreign key value on foreign key to parent model's primary key when child model had different primary key field.
171 lines
4.3 KiB
Python
171 lines
4.3 KiB
Python
"""
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XX. Model inheritance
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Model inheritance exists in two varieties:
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- abstract base classes which are a way of specifying common
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information inherited by the subclasses. They don't exist as a separate
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model.
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- non-abstract base classes (the default), which are models in their own
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right with their own database tables and everything. Their subclasses
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have references back to them, created automatically.
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Both styles are demonstrated here.
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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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#
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# Abstract base classes
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#
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@python_2_unicode_compatible
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class CommonInfo(models.Model):
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name = models.CharField(max_length=50)
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age = models.PositiveIntegerField()
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class Meta:
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abstract = True
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ordering = ['name']
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def __str__(self):
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return '%s %s' % (self.__class__.__name__, self.name)
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class Worker(CommonInfo):
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job = models.CharField(max_length=50)
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class Student(CommonInfo):
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school_class = models.CharField(max_length=10)
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class Meta:
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pass
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class StudentWorker(Student, Worker):
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pass
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#
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# Abstract base classes with related models
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#
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class Post(models.Model):
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title = models.CharField(max_length=50)
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@python_2_unicode_compatible
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class Attachment(models.Model):
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post = models.ForeignKey(Post, related_name='attached_%(class)s_set')
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content = models.TextField()
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class Meta:
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abstract = True
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def __str__(self):
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return self.content
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class Comment(Attachment):
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is_spam = models.BooleanField(default=False)
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class Link(Attachment):
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url = models.URLField()
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#
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# Multi-table inheritance
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#
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@python_2_unicode_compatible
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class Chef(models.Model):
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name = models.CharField(max_length=50)
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def __str__(self):
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return "%s the chef" % self.name
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@python_2_unicode_compatible
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class Place(models.Model):
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name = models.CharField(max_length=50)
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address = models.CharField(max_length=80)
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def __str__(self):
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return "%s the place" % self.name
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class Rating(models.Model):
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rating = models.IntegerField(null=True, blank=True)
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class Meta:
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abstract = True
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ordering = ['-rating']
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@python_2_unicode_compatible
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class Restaurant(Place, Rating):
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serves_hot_dogs = models.BooleanField(default=False)
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serves_pizza = models.BooleanField(default=False)
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chef = models.ForeignKey(Chef, null=True, blank=True)
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class Meta(Rating.Meta):
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db_table = 'my_restaurant'
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def __str__(self):
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return "%s the restaurant" % self.name
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@python_2_unicode_compatible
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class ItalianRestaurant(Restaurant):
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serves_gnocchi = models.BooleanField(default=False)
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def __str__(self):
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return "%s the italian restaurant" % self.name
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@python_2_unicode_compatible
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class Supplier(Place):
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customers = models.ManyToManyField(Restaurant, related_name='provider')
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def __str__(self):
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return "%s the supplier" % self.name
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@python_2_unicode_compatible
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class ParkingLot(Place):
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# An explicit link to the parent (we can control the attribute name).
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parent = models.OneToOneField(Place, primary_key=True, parent_link=True)
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main_site = models.ForeignKey(Place, related_name='lot')
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def __str__(self):
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return "%s the parking lot" % self.name
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#
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# Abstract base classes with related models where the sub-class has the
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# same name in a different app and inherits from the same abstract base
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# class.
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# NOTE: The actual API tests for the following classes are in
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# model_inheritance_same_model_name/models.py - They are defined
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# here in order to have the name conflict between apps
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#
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class Title(models.Model):
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title = models.CharField(max_length=50)
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class NamedURL(models.Model):
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title = models.ForeignKey(Title, related_name='attached_%(app_label)s_%(class)s_set')
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url = models.URLField()
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class Meta:
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abstract = True
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@python_2_unicode_compatible
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class Copy(NamedURL):
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content = models.TextField()
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def __str__(self):
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return self.content
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class Mixin(object):
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def __init__(self):
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self.other_attr = 1
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super(Mixin, self).__init__()
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class MixinModel(models.Model, Mixin):
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pass
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class Base(models.Model):
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titles = models.ManyToManyField(Title)
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class SubBase(Base):
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sub_id = models.IntegerField(primary_key=True)
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