Django-Rest-Framework. Updating nested object

I came across the same problem recently. The way I addressed it was to force the id to be a required field:

class MySerializer(serializers.ModelSerializer):

    class Meta:
        model = MyModel
        fields = ('id', 'name', 'url', )
        extra_kwargs = {'id': {'read_only': False, 'required': True}}

This way I was able to retrieve the correct instance and update it

This is the way I've accomplished the task:

I've added an id field to the InvoiceItemSerializer

class InvoiceItemSerializer(serializers.ModelSerializer):
    ...
    id = serializers.IntegerField(required=False)
    ...

And the update method for the InvoiceSerializer

def update(self, instance, validated_data):
    instance.nr = validated_data.get('nr', instance.nr)
    instance.title = validated_data.get('title', instance.title)
    instance.save()

    items = validated_data.get('items')

    for item in items:
        item_id = item.get('id', None)
        if item_id:
            inv_item = InvoiceItem.objects.get(id=item_id, invoice=instance)
            inv_item.name = item.get('name', inv_item.name)
            inv_item.price = item.get('price', inv_item.price)
            inv_item.save()
        else:
            InvoiceItem.objects.create(account=instance, **item)

    return instance

Also in the create method I'm popping the id if it is passed.

All of these solutions seemed too complex or too specific for me, I ended up using code from the tutorial here which was incredibly simple and reusable:

from rest_framework import serializers
from django.contrib.auth import get_user_model
from myapp.models import UserProfile


# You should already have this somewhere
class UserProfileSerializer(serializers.ModelSerializer):
    class Meta:
        model = UserProfile
        fields = ['nested', 'fields', 'you', 'can', 'edit']


class UserSerializer(serializers.ModelSerializer):
    # CHANGE "userprofile" here to match your one-to-one field name
    userprofile = UserProfileSerializer()

    def update(self, instance, validated_data):
        # CHANGE "userprofile" here to match your one-to-one field name
        if 'userprofile' in validated_data:
            nested_serializer = self.fields['userprofile']
            nested_instance = instance.userprofile
            nested_data = validated_data.pop('userprofile')

            # Runs the update on whatever serializer the nested data belongs to
            nested_serializer.update(nested_instance, nested_data)

        # Runs the original parent update(), since the nested fields were
        # "popped" out of the data
        return super(UserSerializer, self).update(instance, validated_data)

EDIT: Bugfix, I added a check for the nested field's existence before attempting to update it.