Django Rest api json imput for m-m relation

Using Django
1

I am trying to post json file and save the models into database. AttributeName and AttributeValue is generated correctly but Attribute is saved without “nazev_atributu_id” and “hodnota_atributu_id”.

[     
    
  {
    "AttributeName": {
      "id": 2,
      "nazev": "Barva"
    }
  },
  {
    "AttributeValue": {
      "id": 2,
      "hodnota": "modrá"
    }
  },

  {
    "Attribute": {
      "id": 1,
      "nazev_atributu_id": 2,
      "hodnota_atributu_id": 2
    }
  }
]

models.py

from django.db import models


class AttributeValue(models.Model):
    unique_id = models.AutoField(primary_key=True)
    id = models.IntegerField(unique=True)
    hodnota = models.CharField(max_length=255, null=True, blank=True)

    def __str__(self):
        return f"AttributeValue with id: {self.id}"


class AttributeName(models.Model):
    unique_id = models.AutoField(primary_key=True)
    id = models.IntegerField()
    nazev = models.CharField(max_length=255, null=True, blank=True)
    kod = models.CharField(max_length=255, null=True, blank=True)
    zobrazit = models.BooleanField(default=False)

    def __str__(self):
        return f"AttributeName with id: {self.id}"


class Attribute(models.Model):
    unique_id = models.AutoField(primary_key=True)
    id = models.IntegerField(unique=True)
    nazev_atributu_id = models.ManyToManyField(AttributeName, through='AttributeAttributeNameMapping')
    hodnota_atributu_id = models.ManyToManyField(AttributeValue, through='AttributeAttributeValueMapping')

    def __str__(self):
        return f"Attribute with id: {self.id}"


class AttributeAttributeNameMapping(models.Model):
    attribute = models.ForeignKey(Attribute, on_delete=models.CASCADE)
    attribute_name = models.ForeignKey(AttributeName, on_delete=models.CASCADE)

    class Meta:
        unique_together = ('attribute', 'attribute_name')


class AttributeAttributeValueMapping(models.Model):
    attribute = models.ForeignKey(Attribute, on_delete=models.CASCADE)
    attribute_value = models.ForeignKey(AttributeValue, on_delete=models.CASCADE)

    class Meta:
        unique_together = ('attribute', 'attribute_value')

serializer

from rest_framework import serializers
from .models import *

class AttributeNameSerializer(serializers.ModelSerializer):
    class Meta:
        model = AttributeName
        fields = '__all__'


class AttributeValueSerializer(serializers.ModelSerializer):
    class Meta:
        model = AttributeValue
        fields = '__all__'


class AttributeSerializer(serializers.ModelSerializer):
    nazev_atributu_id = serializers.SlugRelatedField(queryset=AttributeName.objects.all(),slug_field='id')
    hodnota_atributu_id = serializers.SlugRelatedField(queryset=AttributeValue.objects.all(),slug_field='id')

    class Meta:
        model = Attribute
        fields = ["unique_id", "id", "nazev_atributu_id", "hodnota_atributu_id"]

    def create(self, validated_data):
        # Extract many-to-many fields from the validated data
        print("**************************")
        print(validated_data)
        print("**************************")
        nazev_atributu_id = validated_data.pop('nazev_atributu_id')
        hodnota_atributu_id = validated_data.pop('hodnota_atributu_id')
        # Create the Attribute instance
        attribute = Attribute.objects.create(**validated_data)
        print("???????????????????")
        print(nazev_atributu_id.__dict__)
        print(hodnota_atributu_id.__dict__)
        print("?????????????")
        print(attribute, type(attribute))
        print(attribute.__dict__)
        print("------------------")
        print(attribute.nazev_atributu_id)
        print(attribute.hodnota_atributu_id)
        print("------------------")
        # Set many-to-many relationships
        attribute.nazev_atributu_id.add(nazev_atributu_id)
        attribute.hodnota_atributu_id.add(hodnota_atributu_id)
        print("////////////////////")
        print(attribute.__dict__)
        print("////////////////////")
        return attribute

But still cant find out why attribute is same before and after

    attribute.nazev_atributu_id.add(nazev_atributu_id)
    attribute.hodnota_atributu_id.add(hodnota_atributu_id)

This is print output after calling post request:

**************************
{'id': 1, 'nazev_atributu_id': <AttributeName: AttributeName with id: 2>, 'hodnota_atributu_id': <AttributeValue: AttributeValue with id: 2>}
**************************
???????????????????
{'_state': <django.db.models.base.ModelState object at 0x000001E7E56E99D0>, 'unique_id': 206, 'id': 2, 'nazev': 'Barva', 'kod': None, 'zobrazit': False}
{'_state': <django.db.models.base.ModelState object at 0x000001E7E56E9070>, 'unique_id': 214, 'id': 2, 'hodnota': 'modrá'}
?????????????
Attribute with id: 1 <class 'api.models.Attribute'>
{'_state': <django.db.models.base.ModelState object at 0x000001E7E56E9310>, 'unique_id': 78, 'id': 1}
------------------
api.AttributeName.None
api.AttributeValue.None
------------------
////////////////////
{'_state': <django.db.models.base.ModelState object at 0x000001E7E56E9310>, 'unique_id': 78, 'id': 1}
////////////////////

views

class LoadJson(viewsets.ModelViewSet):
    def create(self, request):
        post_successful = True
        over_all_result_ok = []
        over_all_result_nok = []
        sorted_json = sort_json_data(request.data, get_model_ordering())
        for item in sorted_json:
            model_type = list(item.keys())[0]
            model_values = list(item.values())[0]
            result = serialize_model(model_type, model_values)
            if result[0] is False:
                post_successful = False
                add_result_into_dict(over_all_result_nok, model_type, result)
            else:
                add_result_into_dict(over_all_result_ok, model_type, result)
        if post_successful:
            return Response({"status": over_all_result_ok}, status=status.HTTP_201_CREATED)
        return Response({"status": over_all_result_nok}, status=status.HTTP_400_BAD_REQUEST)

def get_model_ordering():
    # model_ordering = [
    #     'AttributeName', 'AttributeValue', 'Attribute',
    #     'Product', 'ProductAttributes', 'Image',
    #     'ProductImage', 'Catalog'
    # ]
    model_ordering = [
        'AttributeName', 'AttributeValue', 'Attribute',
    ]
    return model_ordering


def sort_json_data(json_data, model_ordering):
    sorted_list = []
    for process in model_ordering:
        for item in json_data:
            if list(item.keys())[0] == process:
                sorted_list.append(item)
    return sorted_list


def add_result_into_dict(over_all_result, model_type, result):
    over_all_result.append(
        {
            "model_type": model_type,
            "result": result[0],
            "message": result[1]
        }
    )
    return over_all_result


def serialize_model(model_type, model_values):
    serializer_class = SerializersLink().get_serializer_class(model_type)
    if serializer_class:
        serializer = serializer_class(data=model_values)
        if serializer.is_valid():
            serializer.save()
            return True, f"Json data '{model_values}' for model '{model_type}' are correct according serializer"
        else:

            return False, f"Invalid json data '{model_values}' input in model type: '{model_type}'"
    else:
        return False, f"Not implemented model type: '{model_type}'"

class LoadJson(viewsets.ModelViewSet):
    def create(self, request):
        post_successful = True
        over_all_result_ok = []
        over_all_result_nok = []
        sorted_json = sort_json_data(request.data, get_model_ordering())
        for item in sorted_json:
            model_type = list(item.keys())[0]
            model_values = list(item.values())[0]
            result = serialize_model(model_type, model_values)
            if result[0] is False:
                post_successful = False
                add_result_into_dict(over_all_result_nok, model_type, result)
            else:
                add_result_into_dict(over_all_result_ok, model_type, result)
        if post_successful:
            return Response({"status": over_all_result_ok}, status=status.HTTP_201_CREATED)
        return Response({"status": over_all_result_nok}, status=status.HTTP_400_BAD_REQUEST)

class SerializersLink:
    def __init__(self):
        # self._map_dict = {
        #     "AttributeName": AttributeNameSerializer,
        #     "AttributeValue": AttributeValueSerializer,
        #     "Attribute": AttributeSerializer,
        #     "Product": ProductSerializer,
        #     "ProductAttributes": ProductAttributesSerializer,
        #     "Image": ImageSerializer,
        #     "ProductImage": ProductImageSerializer,
        #     "Catalog": CatalogSerializer,
        # }
        self._map_dict = {
            "AttributeName": AttributeNameSerializer,
            "AttributeValue": AttributeValueSerializer,
            "Attribute": AttributeSerializer,
        }

    def get_serializer_class(self, model_name):
        if model_name in self._map_dict:
            return self._map_dict[model_name]
        return False
2

When you’re trying to add nazev_atributu_id and hodnota_atributu_id to the Attribute instance, you’re trying to add the entire instance of AttributeName and AttributeValue respectively. But, in your Attribute model, these fields are defined as ManyToMany fields, which means they should contain a set of instances, not a single instance.