How to filter Many2Many / Generic Relations properly with Q?
- by HWM-Rocker
Hi,
I have 3 Models, the TaggedObject has a GenericRelation with the ObjectTagBridge. And the ObjectTagBridge has a ForeignKey to the Tag Model.
class TaggedObject(models.Model):
"""
class that represent a tagged object
"""
tags = generic.GenericRelation('ObjectTagBridge',
blank=True, null=True)
class ObjectTagBridge(models.Model):
"""
Help to connect a generic object to a Tag.
"""
# pylint: disable-msg=W0232,R0903
content_type = models.ForeignKey(ContentType)
object_id = models.PositiveIntegerField()
content_object = generic.GenericForeignKey('content_type', 'object_id')
tag = models.ForeignKey('Tag')
class Tag(models.Model):
...
when I am attaching a Tag to an Object, I am creating a new ObjectTagBridge and set its ForeignKey tag to the Tag I want to attach. That is working fine, and I can get all Tags that I attached to my Object very easy. But when I want to get (filter) all Objects that have Tag1 and Tag2 I tried to something like this:
query = Q(tags__tag=Tag1) & Q(tags__tag=Tag2)
object_list = TaggedObjects.filter(query)
but now my object_list is empty, because it is looking for TaggedObjects that have one ObjectTagBridge with 2 tag objects, the first with Tag1 and the second with Tag2.
I my application will be more complex Q queries than this one, so I think I need a solution with this Q object. In fact any combination of binary conjunctions, like: (...) and ( (...) or not(...))
How can I filter this correctly? Every answer is welcome, maybe there is also a different way do achieve this.
thx for your help!!!
