Filter Many to Many relation in Django
django, django-models
Solution
`q = bObjects.filter(c_d=d)` //Give me d not defined. but d is an object like c in the object B.
Try this:
from django.db.models import F
q = bObjects.filter(c__d=F('d'))
As for the question from your comment below you can have 1 sql query instead of 100 in those ways:
1) if you can express your selection of A objects in terms of a query (for example a.price<10 and a.weight>20) use this:
B.objects.filter(a__price__lt=10, a__weight__gt=20, c__d=F('d'))
or this:
B.objects.filter(a__in=A.objects.filter(price__lt=10, weight__gt=20), c_d=F('d'))
2) if you just have a python list of A objects, use this:
B.objects.filter(a__pk__in=[a.pk for a in your_a_list], c__d=F('d'))
Problem
I have this structure of model objects: Class A: ``` b = models.ManyToManyField("B") ``` Class B: ``` c = models.ForeignKey("C") d = models.ForeignKey("D") ``` Class C: ``` d = models.ForeignKey("D") ``` This is the query I'm trying to get: I want to get all the B objects of object A, then in each B object to perform a comparison between the D object and the c.d object. I know that simply move on the B collection with for loop and make this comparison. But I dived on the ManyToMany relation, then I noticed I can do the following: ``` bObjects = A.objects.all().b q = bObjects.filter(c__d=None) ``` This is working, it gives me all the c objects with `None` d field. But when I try the following : ``` q = bObjects.filter(c__d=d) ``` It gives me d not defined, but d is an object like c in the object B. What can be the problem? I'll be happy if you suggest further way to do this task. I generally I'm trying to write my query in a single operation with many to many sub objects and not using loops.