Django Manytomany "needs to have a value for field "id" before this Many-to-Many Relationship can be used"

Question

Hello,

I’m trying to assign data in a model that contains a Manytomany field...

Reading around I understood that first should instantiated the Model creating it and passing the data with exception of the Manytomany field.

I am rewriting the create() method but when I try to create initially the way I described, I continue with the same error, the following is displayed:

*** ValueError: "<Cart: XPTO>" needs to have a value for field "id" before this many-to-many relationship can be used.

Here is my code:

Model

from datetime import datetime
from clients.models import Client
from sellers.models import Seller
from itens.models import Item
from django.db import models

class Cart(models.Model):
    client = models.ForeignKey(Client, on_delete=models.CASCADE, blank=True, null=True)
    seller = models.ForeignKey(Seller, on_delete=models.CASCADE, blank=True, null=True)
    itens = models.ManyToManyField(Item, blank=True, null=True)
    datetime = models.DateTimeField(auto_now_add=True)
    total_value = models.DecimalField(max_digits=5, decimal_places=2, null=True, blank=True)
    commission = models.DecimalField(max_digits=5, decimal_places=2, null=True, blank=True)
    
    def __str__(self):
        return str(self.client)

Serialize:

from products.models import Product
from itens.api.serializers import ItemSerializer
from itens.models import Item
from clients.models import Client
from clients.api.serializers import ClientSerializer
from carts.models import Cart
from rest_framework.serializers import ModelSerializer

class CartSerializer(ModelSerializer):
    itens = ItemSerializer(many=True)
    
    class Meta:
        model = Cart
        fields = '__all__'
        
    def create(self, validated_data):
        itens = validated_data['itens']
        del validated_data['itens']
        
        carts = Cart.objects.create(**validated_data)
        

I have also tried to remove other fields from the validated_data as a seller and client to test, but I still have the same error.

It’s like I’m prevented from creating the object anyway.

Someone can give me a boost with that?

Thanks!