在Django的模型中添加自定义方法的示例

这是一项在模型的一个地方集中业务逻辑的技术。

最好用例子来解释一下。 这个模型有一些自定义方法：

from django.contrib.localflavor.us.models import USStateField
from django.db import models

class Person(models.Model):
  first_name = models.CharField(max_length=50)
  last_name = models.CharField(max_length=50)
  birth_date = models.DateField()
  address = models.CharField(max_length=100)
  city = models.CharField(max_length=50)
  state = USStateField() # Yes, this is U.S.-centric...

  def baby_boomer_status(self):
    "Returns the person's baby-boomer status."
    import datetime
    if datetime.date(1945, 8, 1) <= self.birth_date <= datetime.date(1964, 12, 31):
      return "Baby boomer"
    if self.birth_date < datetime.date(1945, 8, 1):
      return "Pre-boomer"
    return "Post-boomer"

  def is_midwestern(self):
    "Returns True if this person is from the Midwest."
    return self.state in ('IL', 'WI', 'MI', 'IN', 'OH', 'IA', 'MO')

  def _get_full_name(self):
    "Returns the person's full name."
    return u'%s %s' % (self.first_name, self.last_name)
  full_name = property(_get_full_name)

例子中的最后一个方法是一个property。 想了解更多关于属性的信息请访问http://www.python.org/download/releases/2.2/descrintro/#property

这是用法的实例：

>>> p = Person.objects.get(first_name='Barack', last_name='Obama')
>>> p.birth_date
datetime.date(1961, 8, 4)
>>> p.baby_boomer_status()
'Baby boomer'
>>> p.is_midwestern()
True
>>> p.full_name # Note this isn't a method -- it's treated as an attribute
u'Barack Obama'