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Fixed #19539 -- Updated custom model fields example for Python 3. 

Thanks astorije@ for the report.
This commit is contained in:
Tim Graham 2013-07-05 06:53:19 -04:00
parent 3e60cc2992
commit b9fceadfd4
1 changed files with 16 additions and 2 deletions
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18
docs/howto/custom-model-fields.txt
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@ -249,7 +249,7 @@ appropriate Python object. The details of how this happens internally are a
little complex, but the code you need to write in your ``Field`` class is little complex, but the code you need to write in your ``Field`` class is
simple: make sure your field subclass uses a special metaclass: simple: make sure your field subclass uses a special metaclass:
For example:: For example, on Python 2::
class HandField(models.Field): class HandField(models.Field):
@ -258,7 +258,21 @@ For example::
__metaclass__ = models.SubfieldBase __metaclass__ = models.SubfieldBase
def __init__(self, *args, **kwargs): def __init__(self, *args, **kwargs):
# ... ...
On Python 3, in lieu of setting the ``__metaclass__`` attribute, add
``metaclass`` to the class definition::
class HandField(models.Field, metaclass=models.SubfieldBase):
...
If you want your code to work on Python 2 & 3, you can use
:func:`six.with_metaclass`::
from django.utils.six import with_metaclass
class HandField(with_metaclass(models.SubfieldBase, models.Field)):
...
This ensures that the :meth:`.to_python` method, documented below, will always This ensures that the :meth:`.to_python` method, documented below, will always
be called when the attribute is initialized. be called when the attribute is initialized.