[Model examples] 自定义模块方法

[憨狗]

Giving models custom methods

在模块中实现的任何方法都可以在实例中使用

Model source code

from django.db import models
import datetime

class Article(models.Model):
headline = models.CharField(maxlength=100)
pub_date = models.DateField()

def __str__(self):
return self.headline

def was_published_today(self):
return self.pub_date == datetime.date.today()

def articles_from_same_day_1(self):
return
Article.objects.filter(pub_date=self.pub_date).exclude(id=self.id)

def articles_from_same_day_2(self):
"""
Verbose version of get_articles_from_same_day_1, which does a custom
database query for the sake of demonstration.
"""
from django.db import connection
cursor = connection.cursor()
cursor.execute("""
SELECT id, headline, pub_date
FROM custom_methods_article
WHERE pub_date = %s
AND id != %s""", [str(self.pub_date), self.id])
# The asterisk in "(*row)" tells Python to expand the list into
# positional arguments to Article().
return [self.__class__(*row) for row in cursor.fetchall()]

Sample API usage

上面的代码在 bare_bones/models.py里面.

>>> from mysite.models import Article

# 新建一些文章.
>>> from datetime import date
>>> a = Article(id=None, headline='Area man programs in Python', pub_date=date(2005, 7, 27))
>>> a.save()
>>> b = Article(id=None, headline='Beatles reunite', pub_date=date(2005, 7, 27))
>>> b.save()

# 测试自定义的方法.
>>> a.was_published_today()
False
>>> a.articles_from_same_day_1()
[<Article: Beatles reunite>]
>>> a.articles_from_same_day_2()
[<Article: Beatles reunite>]
>>> b.articles_from_same_day_1()
[<Article: Area man programs in Python>]
>>> b.articles_from_same_day_2()
[<Article: Area man programs in Python>]