The Cast function is used in Django to cast a value to a different data type. In the provided code, Cast is used to cast the organization.id value to an IntegerField(). This is necessary because the total_orders field is being annotated with a count of related orders, which requires an IntegerField data type. However, the organization.id value is not an IntegerField, so it needs to be casted before it can be used in the Count function.

Here's an example of using Cast in Django:

from django.db.models import Cast, IntegerField

users = User.objects.annotate(
    age_int=Cast("age", IntegerField())
).filter(age_int__gte=18)

In the example above, the Cast function is used to cast the age field to an IntegerField. This allows us to use the age_int field in our filter, which requires an IntegerField.

Here's an edited version of the code:

from django.db.models import Cast, IntegerField

users = User.objects.annotate(
    total_orders=Count("orders"),
    organization=Cast(organization.id, IntegerField()),
).filter(organization=1, total_orders__gte=10)

This code retrieves all users who have an organization ID of 1 and have at least 10 related orders. The organization.id value is casted to an IntegerField using the Cast function before being used in the filter function.

class PrivateCustomerList(ListAPIView):
    serializer_class = PrivateCustomerSerializer
    permission_classes = [permissions.IsOrganizationStaff]
    filter_backends = [filters.SearchFilter]
    search_fields = ["first_name", "last_name", "phone"]

    def get_queryset(self):
        organization = self.request.user.get_organization()
        users = (
            User.objects.annotate(
                total_orders=Count("orders"),
                organization=Cast(organization.id, IntegerField()),
            )
            .prefetch_related("organizationuser_set")  # Use default related name
            .filter(
                organizationuser__organization=organization,
                organizationuser__role=OrganizationUserRole.CUSTOMER,
            )
            .order_by("-created_at")
        )
        statuses = self.request.query_params.getlist("statuses", [""])
        if statuses[0]:
            users = users.filter(organizationuser__status__in=statuses)

        return users

class PrivateCustomerSerializer(serializers.ModelSerializer):
    total_orders = serializers.IntegerField(read_only=True)
    discount_offset = serializers.SerializerMethodField(read_only=True)
    role = serializers.SerializerMethodField(read_only=True)

    class Meta:
        model = User
        fields = [
            "uid",
            "first_name",
            "last_name",
            "phone",
            "discount_offset",
            "role",
            "total_orders",
            "created_at",
        ]
        read_only_fields = ("__all__",)

    def get_discount_offset(self, user):
        organization_id = user.organization
        organization_user = get_object_or_404(
            user.organizationuser_set.filter(), organization_id=organization_id
        )
        if organization_user:
            return organization_user.discount_offset
        return None

    def get_role(self, user):
        organization_id = user.organization
        organization_user = get_object_or_404(
            user.organizationuser_set.filter(), organization_id=organization_id
        )
        if organization_user:
            return organization_user.role
        return None