在Django中，通过外键选择相关字段

Question

I am aware of that to select a related object one should do object.related_set.all() . Yet in my situation this produces an AttributeError, so it's very hard to debug. Here is the setup:

class Action(models.Model):
    ...

class FieldDiff(models.Model):
    action = models.ForeignKey(Action, editable=False, related_name='Action')

And in a shell:

In [16]: act = Action.objects.get(pk=34)
In [17]: act.fielddiff_set.all()
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)

/home/ipantuyev/progs/ccc_app/<ipython console> in <module>()

AttributeError: 'Action' object has no attribute 'fielddiff_set'

I suppose this has to do with translation from camelcase. I can go around this, but this code would be called from the template, so I would rather have no extra logic.

Answer 1

This is because you specified related_name to be Action . This means you want to access all FieldDiff instances associated with an Action via Action_set . Since it seems like this isn't what you want, the simplest solution is to remove the related_name parameter.

Answer 2

This has nothing to do with "translation from camelcase".

You have given your ForeignKey an explicit related_name attribute. This is the name that Django uses to provide the reverse relationship. So your query should be:

act.Action.all()

Actually, that related_name value makes no sense. You should remove it, then the original fielddiff_set would work.