django/tests/foreign_object/models/article.py

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from django.db import models
from django.db.models.fields.related import ForwardManyToOneDescriptor
from django.utils.translation import get_language
class ArticleTranslationDescriptor(ForwardManyToOneDescriptor):
"""
The set of articletranslation should not set any local fields.
"""
def __set__(self, instance, value):
if instance is None:
raise AttributeError("%s must be accessed via instance" % self.field.name)
setattr(instance, self.cache_name, value)
if value is not None and not self.field.remote_field.multiple:
setattr(value, self.field.related.get_cache_name(), instance)
class ColConstraint:
# Anything with as_sql() method works in get_extra_restriction().
def __init__(self, alias, col, value):
self.alias, self.col, self.value = alias, col, value
def as_sql(self, compiler, connection):
qn = compiler.quote_name_unless_alias
return '%s.%s = %%s' % (qn(self.alias), qn(self.col)), [self.value]
class ActiveTranslationField(models.ForeignObject):
"""
This field will allow querying and fetching the currently active translation
for Article from ArticleTranslation.
"""
requires_unique_target = False
def get_extra_restriction(self, where_class, alias, related_alias):
return ColConstraint(alias, 'lang', get_language())
def get_extra_descriptor_filter(self, instance):
return {'lang': get_language()}
def contribute_to_class(self, cls, name):
super().contribute_to_class(cls, name)
setattr(cls, self.name, ArticleTranslationDescriptor(self))
class ActiveTranslationFieldWithQ(ActiveTranslationField):
def get_extra_descriptor_filter(self, instance):
return models.Q(lang=get_language())
class Article(models.Model):
active_translation = ActiveTranslationField(
'ArticleTranslation',
from_fields=['id'],
to_fields=['article'],
related_name='+',
on_delete=models.CASCADE,
null=True,
)
active_translation_q = ActiveTranslationFieldWithQ(
'ArticleTranslation',
from_fields=['id'],
to_fields=['article'],
related_name='+',
on_delete=models.CASCADE,
null=True,
)
pub_date = models.DateField()
def __str__(self):
try:
return self.active_translation.title
except ArticleTranslation.DoesNotExist:
return '[No translation found]'
class NewsArticle(Article):
pass
class ArticleTranslation(models.Model):
article = models.ForeignKey(Article, models.CASCADE)
lang = models.CharField(max_length=2)
title = models.CharField(max_length=100)
body = models.TextField()
abstract = models.CharField(max_length=400, null=True)
class Meta:
unique_together = ('article', 'lang')
ordering = ('active_translation__title',)
class ArticleTag(models.Model):
article = models.ForeignKey(
Article,
models.CASCADE,
related_name='tags',
related_query_name='tag',
)
name = models.CharField(max_length=255)
class ArticleIdea(models.Model):
articles = models.ManyToManyField(
Article,
related_name='ideas',
related_query_name='idea_things',
)
name = models.CharField(max_length=255)