On Feb 2, 12:11 am, Peter Otten <__pete...@web.de> wrote:
> Marc Aymerich wrote:
> > Hi all,
> > I want to provide an encapsulated static attribute called _registry
> > for several classes.
>
> > I try to use inheritance in order to make it DRY: all classes inherit
> > from a BaseClass that implements the _registry encapsulation. But with
> > inheritance it doesn't work how I want, because a single instance of
> > the _registry is shared between all of the inherited classes, and I
> > want to have an independent _registry for every class.
>
> > How can I do that without coping all the code in every class?
>
> If you want to go fancy use a metaclass:
>
> >>> class Base(object):
>
> ... class __metaclass__(type):
> ... def __init__(self, *args):
> ... type.__init__(self, *args)
> ... self.per_class = []
> ...>>> class A(Base): pass
> ...
> >>> A().per_class is A().per_class
> True
> >>> class B(Base): pass
> ...
> >>> B().per_class is B().per_class
> True
> >>> A().per_class is B().per_class
>
> False
Hi!,
Unfortunately per_class attribute losses the "independence" when I try
to mix it with django models.Model .
from django.db import models
class Plugin(models.base.ModelBase):
class __metaclass__(type):
def __init__(self, *args):
type.__init__(self, *args)
self.per_class = []
class BaseService(models.Model):
class Meta:
abstract = True
__metaclass__ = Plugin
class VirtualHost(BaseService):
name = models.CharField(max_length=10)
class SystemUser(BaseService):
name = models.CharField(max_length=10)
>>> VirtualHost.per_class is SystemUser.per_class
True
What am I doing wrong?
Thanks again!
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