CODEWITHSUNDEEP
djangodjango-modelsdjango-queryset
Llanilek
Llanilek

Reputation: 3466

Figuring out a relation for queryset

I currently have a few models that either do or don't directly relate to a user. User Region and Location.

User is related to Location through a ForeignKey manager and Region is related to Location through a ForeignKey region.

My question is what would be the correct queryset to show the relationship between the User and the Region for example if I were to return all the Regions that belonged to a certain user.

class Region(models.Model):
    name = models.CharField(max_length=255)
    ...

class Location(models.Model):
    region = models.ForeignKey(Region, blank=True, null=True)
    manager = models.ForeignKey(User, blank=True, null=True)
    ...

I want to try and avoid having a direct relationship between User and Region if I can help it.

Upvotes: 2

Views: 39

Answers (1)

karthikr
karthikr

Reputation: 99630

Assuming the user variable is a User instance,

You can have a lookup like this:

 regions = Region.objects.filter(location__user=user)

Basically, for the reverse foreign key relationship in the queryset, you would use the lowercase modelname for the field lookup - location in this case.

If such a relationship does not exist, regions.count() would be 0

Documentation of this feature is here

Another way of achieving this is,

regions = user.location_set.values('region') #or values_list - or however you want this

Upvotes: 4

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