Question

I have created a model which has foreign key to the django.contrib.auth.models User model. I need to retrieve the value the foreign key is referring to. But how to do that?

E.g. my model is

from django.contrib.auth.models import User
def FooModel(models.Model):
      user = models.ForeignKey(User)

then I know I can either use:

FooModel.objects.get() or FooModel.objects.filter() but as far as I know they will only return entries from the FooModel only. So how do I retrieve from the User model?

Answer 1

m = FooModel.objects.get(id=123434)
m.user.username

You can use ..That wxample will return you the username of the related user. Also you can create joins using __ on the query filtering. Like:

FooModel.objects.get(user__username='Foo')

But, since you are building your query on FooModel, you will always get FooModel results. So you have you use . to use foreignkey relations to get to the required User field.

EDIT:

Django also allows you to use reverse relations on querysets, so even though User model do not have a foreignkey to FooModel on its model structure, you can use reverse relation of Foomodel.user foreignkey like:

def FooModel(models.Model):
    user = models.ForeignKey(User)
    foofield = Models.CharField(...)



User.objects.get(foomodel__foofield='Beatles')

will return you the user which have FooModel record with a foreign key to his User record and foofield value of Beatles