Get fields from through table in Django - django

Question

I have two models, organization and vendor, which are connected by a 'relational' or 'through' table, VendorOrganization. There is a field description in my through table, which I am trying to access, but do not know. How should I configure my view, query and serializer to be able to access fields from the through table? Thanks for any help!
// models.py
class Organization(models.Model):
id = models.AutoField(primary_key=True)
name = models.CharField(max_length=20, unique=True, validators=[alphanumeric_plus_underscore, MinLengthValidator(4)])
vendors = models.ManyToManyField("thirdparty.Vendor", through="thirdparty.VendorOrganization")
class Vendor(models.Model):
id = models.AutoField(primary_key=True)
name = models.CharField(max_length=60, blank=False, null=False)
class VendorOrganization(models.Model):
vendor = models.ForeignKey(Vendor, blank=False, null=False, on_delete=models.CASCADE)
organization = models.ForeignKey(Organization, blank=True, null=False, on_delete=models.DO_NOTHING)
created_at = models.DateTimeField(_('created at'), auto_now_add=True, null=True)
created_by_user = models.ForeignKey(User, blank=False, null=False, on_delete=models.DO_NOTHING)
description = models.CharField(max_length=300, blank=True, null=False)
// serializers.py (this does not work to get the 'description' field)
class VendorSerializer(serializers.ModelSerializer):
class Meta:
model = Vendor
fields = ('id', 'name', 'created_at', 'created_by_user', 'description')
extra_kwargs = {
'id': {'read_only': True},
'created_at': {'read_only': True},
}
// views.py
class VendorView(mixins.DestroyModelMixin, ListAPIView):
authentication_classes = (TokenAuthentication,)
def get(self, request):
pagination_class = None
current_org = Organization.objects.get(id=request.user.organization.id)
queryset = current_org.vendors.select_related()
vendors = VendorSerializer(queryset, many=True)
return Response(vendors.data)

Answer 1

You can pass your organization_id with context to your serializer and in serializer, use SerializerMethodField(). Like that
in your views.py:
class VendorView(mixins.DestroyModelMixin, ListAPIView):
#your other codes
#add this method for pass data to your serializer
def get_serializer_context(self):
return {'organization_id': request.user.organization.id}
in your serializers.py file
class VendorSerializer(serializers.ModelSerializer):
description = serializers.SerializerMethodField()
class Meta:
model = Vendor
fields = ('id', 'name', 'created_at', 'created_by_user', 'description')
extra_kwargs = {
'id': {'read_only': True},
'created_at': {'read_only': True},
}
def get_description(self,obj):
organization = Organization.objects.get(id=self.context['organization_id'])
return obj.vendororganization_set.filter(organization=organization).first().description()
#NOTE: You can have multiple vendororganization, so you must set a logic in here.Perhaps you can change your vendor model with OneToOneFieldAnd you must check whether your vendor organziation exists.

Answer 2

In serializer.py change the model from Vendor to VendorOrganization. Because you are referencing both through that model