Django REST: queryset error type error int() must be a string

Question

I'm trying to get all users who are employers. So what I did was I filter the users where the id can be found in the "employer" field of any (other) user. However this gives me the following error:

TypeError: int() argument must be a string, a bytes-like object or a number, not 'builtin_function_or_method'

View:

# Get all employers
class Employers(viewsets.ModelViewSet):
    queryset = CustomUser.objects.all()
    serializer_class = CustomUserSerializer

    def list(self, request):
        #queryset = CustomUser.objects.all();
        queryset = self.queryset.filter(id__in=CustomUser.objects.filter(employer=id))    #this gives me an error
        serializer = CustomUserSerializer(queryset, many=True)
        return Response(serializer.data)

Model (standard stuff):

# CustomUser model
class CustomUser(AbstractBaseUser):
    username = None
    email = models.EmailField(verbose_name='email address', max_length=255, unique=True)
    date_joined = models.DateTimeField(verbose_name='date joined', auto_now_add=True)
    last_login = models.DateTimeField(verbose_name='last login', auto_now=True)
    is_admin = models.BooleanField(default=False)
    is_active = models.BooleanField(default=True)
    is_staff = models.BooleanField(default=False)
    is_superuser = models.BooleanField(default=False)

    employer = models.ForeignKey("self", blank=True, null=True, on_delete=models.DO_NOTHING)

    USERNAME_FIELD = 'email'
    REQUIRED_FIELDS = []

    objects = MyUserManager()

    def __str__(self):
        return self.email

    def has_perm(self, perm, obj=None):
        return self.is_admin

    def has_module_perms(selfself, app_label):
        return True;

I'm not sure what I'm doing wrong. Any suggestions?

what you are passing in id where the error occurs. I mean int or object? — Pruthvi Barot
– Pruthvi Barot, Commented Jul 23, 2020 at 10:55
@PruthviBarot: the builtin id function: docs.python.org/3/library/functions.html#id — willeM_ Van Onsem
– willeM_ Van Onsem, Commented Jul 23, 2020 at 11:14

willeM_ Van Onsem · Accepted Answer · 2020-07-23 11:29:17Z

1

You can filter with an F-expression [Django-doc] to refer to another column:

from django.db.models import F

class Employers(viewsets.ModelViewSet):
    queryset = CustomUser.objects.all()
    serializer_class = CustomUserSerializer

    def get_queryset(self, *args, **kwargs):
        return CustomUser.objects.filter(employer=F('pk'))

This thus makes a query that looks like;

SELECT customuser.*
FROM customuser
WHERE customuser.employer = customuser.id

or you can filter the relation in reverse to get CustomUsers that employ at least one person:

class Employers(viewsets.ModelViewSet):
    queryset = CustomUser.objects.all()
    serializer_class = CustomUserSerializer

    def get_queryset(self, *args, **kwargs):
        return CustomUser.objects.filter(customuser__isnull=False).distinct()

This constructs a query that looks like:

SELECT DISTINCT customuser.*
FROM customuser
JOIN customuser u2 ON u2.employer = customuser.id

edited Jul 23, 2020 at 11:29

answered Jul 23, 2020 at 11:04

willeM_ Van Onsem

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7 Comments

SJ19 Over a year ago

Thanks for your answer but I think this query isn't correct? Correct me if I'm wrong but I think this query selects customusers where their employer is the same as their id. So you only get the users who are their own employer? Whereas I simply want all employers.

willeM_ Van Onsem Over a year ago

@SJ19: in that case it is the latter. The question is, what are the employes of an employer? I would think then it refers to itself. But the second query lists all CustomUsers who have at least one CustomUser that has them as employer.

SJ19 Over a year ago

Employers don't have employers (null) :). Second query works! But I honestly have no clue what you're doing here, care to explain? Like what does customuser__isnull=False do, and what is distinct? There doesn't seem to be any reference to the employer field which I don't get.

willeM_ Van Onsem Over a year ago

@SJ19: no, but then it would perhaps be more elegant to link it to themselves, since then it is not a NULLable field, and moving "up" in the hierarcy is thus more elegant. Anyway, the latter should produce customusers that have at least one employee.

willeM_ Van Onsem Over a year ago

@SJ19: it means we make a LEFT OUTER join on the employer relation in reverse, and because of the __isnull=False filter, it thus is a simle INNER JOIN. The .distinct() is necessary, since otherwise we would return the same CustomUser multiple times, one for each employee.

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