Hi everyone,
I apologise for the verbosity of this message - for my first post it's
quite long.
I am currently working on my first project employing the Sites
framework, and have been moving along quite well with the
documentation until I hit a snag last night.
I have overloaded the default manager in my model to use a slight
variant of the CurrentSiteManager, shown below.
class MyCurrentSiteManager(models.Manager):
def __init__(self, field_name='site'):
super(MyCurrentSiteManager, self).__init__()
self.__field_name = field_name
def get_query_set(self):
return super(MyCurrentSiteManager,
self).get_query_set().filter(**{self.__field_name + '__id__exact':
settings.SITE_ID})
The reason I've trimmed it down, is because I want field_name to be a
site reference on a related model. such as:
class Venue(models.Model):
name = models.CharField(max_length=50)
site = models.ForeignKey(Site)
objects = MyCurrentSiteManager()
systemwide = models.Manager()
class Conference(models.Model):
title = models.CharField(max_length=50)
venue = models.ForeignKey(Venue, related_name='conferences')
objects = MyCurrentSiteManager('venue__site')
systemwide = models.Manager()
What I am seeing is that the following queries work and present only
the objects which are on the site (Venue) or objects which are related
to a Venue on the site (Conference):
Venue.objects.all()
Conference.objects.all()
However, if I try to get the related objects of a Venue object, I get
an error as below:
>>> v = Venue.objects.get(pk=1)
>>> v.conferences.all()
Traceback (most recent call last):
File "<console>", line 1, in <module>
File "/usr/lib/python2.5/site-packages/django/db/models/manager.py",
line 78, in all
return self.get_query_set()
File "/usr/lib/python2.5/site-packages/django/db/models/fields/
related.py", line 300, in get_query_set
return
superclass.get_query_set(self).filter(**(self.core_filters))
File "/path/munged/managers.py", line 14, in get_query_set
return super(MyCurrentSiteManager,
self).get_query_set().filter(**{self.__field_name + '__id__exact':
settings.SITE_ID})
File "/usr/lib/python2.5/site-packages/django/db/models/query.py",
line 483, in filter
return self._filter_or_exclude(False, *args, **kwargs)
File "/usr/lib/python2.5/site-packages/django/db/models/query.py",
line 501, in _filter_or_exclude
clone.query.add_q(Q(*args, **kwargs))
File "/usr/lib/python2.5/site-packages/django/db/models/sql/
query.py", line 1224, in add_q
can_reuse=used_aliases)
File "/usr/lib/python2.5/site-packages/django/db/models/sql/
query.py", line 1099, in add_filter
negate=negate, process_extras=process_extras)
File "/usr/lib/python2.5/site-packages/django/db/models/sql/
query.py", line 1287, in setup_joins
"Choices are: %s" % (name, ", ".join(names)))
FieldError: Cannot resolve keyword 'site' into field. Choices are:
venue, id, title
I added a print line to my manager's get_query_set method, so it now
reads:
def get_query_set(self):
print self.model._meta.object_name, self.__field_name
return super(MyCurrentSiteManager,
self).get_query_set().filter(**{self.__field_name + '__id__exact':
settings.SITE_ID})
When I redo the query above, I now get:
>>> v.conferences.all()
Venue site
Conference site
Traceback (most recent call last):
... as before ...
I was expecting it to be:
>>> v.conferences.all()
Venue site
Conference venue__site
<QuerySet>
So my analysis is that the RelatedManager (v.conferences) is not
completely partnering up with my MyCurrentSiteManager because,
although the print statements are firing off, they are not actually
using the field_name parameter I supplied when instantiating the
manager on the model.
And here we are, finally at my question! Is it possible to have the
related manager use the field_name that was passed in to my custom
manager?
Again, sorry for the long post but I thought it best to lay it all out
there first!
Regards,
Gary
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