1 """

     2 32. Callable defaults

     3 

     4 You can pass callable objects as the ``default`` parameter to a field. When

     5 the object is created without an explicit value passed in, Django will call

     6 the method to determine the default value.

     7 

     8 This example uses ``datetime.datetime.now`` as the default for the ``pub_date``

     9 field.

    10 """

    11 

    12 from django.db import models

    13 from datetime import datetime

    14 

    15 class Article(models.Model):

    16     headline = models.CharField(maxlength=100, default='Default headline')

    17     pub_date = models.DateTimeField(default=datetime.now)

    18 

    19     def __str__(self):

    20         return self.headline

    21 

    22 __test__ = {'API_TESTS':"""

    23 >>> from datetime import datetime

    24 

    25 # No articles are in the system yet.

    26 >>> Article.objects.all()

    27 []

    28 

    29 # Create an Article.

    30 >>> a = Article(id=None)

    31 

    32 # Grab the current datetime it should be very close to the default that just

    33 # got saved as a.pub_date

    34 >>> now = datetime.now()

    35 

    36 # Save it into the database. You have to call save() explicitly.

    37 >>> a.save()

    38 

    39 # Now it has an ID. Note it's a long integer, as designated by the trailing "L".

    40 >>> a.id

    41 1L

    42 

    43 # Access database columns via Python attributes.

    44 >>> a.headline

    45 'Default headline'

    46 

    47 # make sure the two dates are sufficiently close

    48 >>> d = now - a.pub_date

    49 >>> d.seconds < 5

    50 True

    51 """}