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"""
Specifying ordering
Specify default ordering for a model using the ``ordering`` attribute, which
should be a list or tuple of field names. This tells Django how to order
``QuerySet`` results.
If a field name in ``ordering`` starts with a hyphen, that field will be
ordered in descending order. Otherwise, it'll be ordered in ascending order.
The special-case field name ``"?"`` specifies random order.
The ordering attribute is not required. If you leave it off, ordering will be
undefined -- not random, just undefined.
"""
from django.db import models
from django.db.models.expressions import OrderBy
class Author(models.Model):
name = models.CharField(max_length=63, null=True, blank=True)
class Meta:
ordering = ('-pk',)
class Article(models.Model):
author = models.ForeignKey(Author, models.SET_NULL, null=True)
second_author = models.ForeignKey(Author, models.SET_NULL, null=True, related_name='+')
headline = models.CharField(max_length=100)
pub_date = models.DateTimeField()
class Meta:
ordering = (
'-pub_date',
'headline',
models.F('author__name').asc(),
OrderBy(models.F('second_author__name')),
)
def __str__(self):
return self.headline
class OrderedByAuthorArticle(Article):
class Meta:
proxy = True
ordering = ('author', 'second_author')
class OrderedByFArticle(Article):
class Meta:
proxy = True
ordering = (models.F('author').asc(nulls_first=True), 'id')
class Reference(models.Model):
article = models.ForeignKey(OrderedByAuthorArticle, models.CASCADE)
class Meta:
ordering = ('article',)
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