On Mar 11, 8:34 pm, Alex Gaynor <alex.gay...@gmail.com> wrote:
> On Wed, Mar 11, 2009 at 10:32 AM, koranthala <koranth...@gmail.com> wrote:
>
> > Hi,
> > I have created an Identity Mapper for my website - which is as
> > follows:
>
> > class IdentityMap(object):
> > def __getattr__(self, name):
> > if not hasattr(self, name):
> > setattr(self, name, {})
> > return getattr(self, name)
>
> > MAP = IdentityMap()
>
> > class MapManager(models.Manager):
> > def get(self, *args, **kwargs):
> > if kwargs.has_key('mapname'):
> > parm = kwargs.pop('mapname')
> > dval = getattr(MAP, self.model.__name__)
> > if not dval.has_key(parm):
> > dval[parm] = super(MapManager, self).get(*args,
> > **kwargs)
> > return dval[parm]
> > else:
> > return super(MapManager, self).get(*args, **kwargs)
>
> > #Model which is overriden by all models
> > class BaseModel(models.Model):
> > objects = MapManager()
>
> > class Meta:
> > abstract = True
>
> > #--------------------------------------------------------------------------
> > ------
> > #
> > Everytime a get is issued (due to lazy loading I did not implement the
> > same for filter), it first checks whether the given mapname is already
> > stored inside MAP, and if not only then will it issue a proper get.
> > Mapname is given by the user - he can give any unique name to it.
>
> > Now, I wanted to do it for all models. Since User is part of
> > django.auth, I overrode User too as given below.
>
> > from django.contrib.auth.models import User, UserManager
>
> > class MyUserManager(UserManager):
> > def get(self, *args, **kwargs):
> > if kwargs.has_key('mapname'):
> > parm = kwargs.pop('mapname')
> > dval = getattr(MAP, self.model.__name__)
> > if not dval.has_key(parm):
> > dval[parm] = super(MyUserManager, self).get(*args,
> > **kwargs)
> > return dval[parm]
> > else:
> > return super(MyUserManager, self).get(*args, **kwargs)
>
> > class MyUser(User):
> > objects = MyUserManager()
>
> > class Meta:
> > abstract = True
>
> > #--------------------------------------------------------------------------
> > ------
> > #
>
> > But when I issued a get on MyUser, it is failing with the following
> > error
>
> > File "C:\django\My\..\My\test\test.py", line 164, in UserData
> > data.save(form)
> > File "C:\django\My\..\My\test\models.py", line 361, in save
> > self.user = MyUser.objects.find(form.cleaned_data['user'],
> > username=form.cleaned_data['user'])
> > File "C:\django\My\..\My\test\models.py", line 93, in find
> > dval[parm] = self.get(*args, **kwargs)
> > File "C:\Python24\Lib\site-packages\django\db\models\manager.py",
> > line 93, in get
> > return self.get_query_set().get(*args, **kwargs)
> > File "C:\Python24\Lib\site-packages\django\db\models\query.py", line
> > 337, in get
> > num = len(clone)
> > File "C:\Python24\Lib\site-packages\django\db\models\query.py", line
> > 161, in __len__
> > self._result_cache = list(self.iterator())
> > File "C:\Python24\Lib\site-packages\django\db\models\query.py", line
> > 281, in iterator
> > for row in self.query.results_iter():
> > File "C:\Python24\Lib\site-packages\django\db\models\sql\query.py",
> > line 254, in results_iter
> > for rows in self.execute_sql(MULTI):
> > File "C:\Python24\Lib\site-packages\django\db\models\sql\query.py",
> > line 2011, in execute_sql
> > sql, params = self.as_sql()
> > File "C:\Python24\Lib\site-packages\django\db\models\sql\query.py",
> > line 362, in as_sql
> > out_cols = self.get_columns(with_col_aliases)
> > File "C:\Python24\Lib\site-packages\django\db\models\sql\query.py",
> > line 588, in get_columns
> > col_aliases)
> > File "C:\Python24\Lib\site-packages\django\db\models\sql\query.py",
> > line 633, in get_default_columns
> > root_pk = opts.pk.column
> > AttributeError: 'NoneType' object has no attribute 'column'
>
> > I even tried changing the metaclass, but it does not seem to have any
> > effect.
> > Can someone help me out?
>
> There was a feature just implemented in the development version that is
> perfect for
> this.http://docs.djangoproject.com/en/dev/ref/models/options/#managed
>
> Alex
>
> --
> "I disapprove of what you say, but I will defend to the death your right to
> say it." --Voltaire
> "The people's good is the highest law."--Cicero
Thank you very much. I will try it out with managed=False.
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