Moved foreign_object models.py into a module.

tests/foreign_object/models/article.py

@@ -0,0 +1,99 @@
+from django.db import models
+from django.db.models.fields.related import \
+    ReverseSingleRelatedObjectDescriptor
+from django.utils.encoding import python_2_unicode_compatible
+from django.utils.translation import get_language
+
+
+class ArticleTranslationDescriptor(ReverseSingleRelatedObjectDescriptor):
+    """
+    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(object):
+    # 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(ActiveTranslationField, self).contribute_to_class(cls, name)
+        setattr(cls, self.name, ArticleTranslationDescriptor(self))
+
+
+@python_2_unicode_compatible
+class Article(models.Model):
+    active_translation = ActiveTranslationField(
+        '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)