Disable update_or_create for ManyToMany nested relations

[spokzers]

Hi,

Is there a way to disable the update_or_create relation for ManyToMany relations ?

for example models.py

from django.db import models

class Skill(models.Model):
      name = models.CharField()

class Profile(models.Model):
    first_name = models.CharField()
    last_name = models.CharField()
    skills = models.ManyToManyField(Skill)

serializers.py

from rest_framework import serializers
from drf_writable_nested import WritableNestedModelSerializer

class SkillSerializer(serializers.ModelSerializer):
    url = serializers.CharField()

    class Meta:
        model = Skill
        fields = ('pk')

class ProfileSerializer(WritableNestedModelSerializer):
    skills = SkillSerializer(many=True)

    class Meta:
        model = Profile
        fields = ('pk', 'skills', 'first_name', 'last_name')

data = {
  "profile": {
  "first_name": "David",
  "last_name": "Hasselhoff",
  "skills": [
      {
        "pk": 1
      },
      {
        "pk": 14
      }
    ]
  }
}

when we send in the above data, it first creates the skills then creates the relation in the bridge table. I want it to throw an Error or just simply refuse to save any data in the database, if the skills do not already exist in the database.

Any idea how I can do that ?

[oguzhancelikarslan]

how can I deal with this problem? @claytondaley @spokzers

[claytondaley]

My answer is not "official" yet, but the PR I linked is intended to let you define behavior per-nested-serializer. This should make it possible to define each nested serializers as a different combinations of get/update and/or create. If you want to use the PR (or branch on my end), I can help you with use/troubleshooting. You should start by looking at the new-style serializers in the test cases to see how they're used/different.

[claytondaley]

FWIW it occurs to me that there are no examples of GetOrCreate since I was just replicating the existing behavior, but it's just a different mixin.

[oguzhancelikarslan]

My answer is not "official" yet, but the PR I linked is intended to let you define behavior per-nested-serializer. This should make it possible to define each nested serializers as a different combinations of get/update and/or create. If you want to use the PR (or branch on my end), I can help you with use/troubleshooting. You should start by looking at the new-style serializers in the test cases to see how they're used/different.

Thank you so much! You are doing great. I only need to update my many to many to data but if i add extra dict into JSON and make the request. it turns out creating new record while updating others. I just want to make update.

[MatejMijoski]

@oguzhancelikarslan Did you solve this? Not sure why there's not an option to update the M2M field if it already exists.