Django DRF - Updating many-to-one model in serializer - django

Question

My models structure is pretty straightforward: a many to one relationship where a set of Conditions references one Item by the foreign key.
And here we have the corresponding serializers.py:
class ConditionSerializer(serializers.ModelSerializer):
class Meta:
model = Condition
fields = ('condition_id','name', 'left', 'operator', 'right')
class ItemSerializer(serializers.ModelSerializer):
conditions = ConditionSerializer(many=True, read_only=True)
def create(self, validated_data):
conditions_data = validated_data.pop("conditions")
item = Item.objects.create(**validated_data)
for condition_data in conditions_data:
Condition.objects.create(item=item, **condition_data)
return item
def update(self, instance, validated_data):
instance.name = validated_data.get('name', instance.name)
conditions_data = validated_data.get('conditions', instance.conditions)
for c in conditions_data.all():
print(c.name) # it correctly prints out the value
instance.conditions.set(conditions_data.all()) # Doesn't update the instance
instance.save()
return instance
class Meta:
model = Item
fields = ('item_id', 'name', 'conditions')
The problem is in the update function:
instance.name is correctly updated; instance.conditions.set(conditions_data.all()) is not.
No error is displayed, since the response is 200OK.
I also put the for loop printing of field of the Condition object (name) and it successfully is displayed, showing that the data is correctly read.
I've tried to address the issue removing the read_only=True from the ConditionSerializer, but the situation got worse since I receive the error:
AttributeError: 'list' object has no attribute 'all'
Maybe the issue is related to the foreign key management.
Is there a way to solve this?
UPDATE: here the models
class Item(models.Model):
item_id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False, unique=True)
created_on = models.DateTimeField(auto_now_add=True, editable=False)
last_updated = models.DateTimeField(auto_now=True, editable=False)
name = models.CharField(max_length=64)
readonly_fields=['item_id','created_on','last_updated']
class Condition(models.Model):
condition_id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False, unique=True)
name = models.CharField(max_length=128)
left = models.JSONField()
operator = models.CharField(max_length=2)
right = models.JSONField()
item = models.ForeignKey(Item, related_name="conditions", on_delete=models.CASCADE, null=True)

Answer 1

I think you need to set their ids.
class ItemSerializer(serializers.ModelSerializer):
conditions = ConditionSerializer(many=True, read_only=True)
...
def update(self, instance, validated_data):
instance.name = validated_data.get('name', instance.name)
conditions_data = validated_data.get('conditions', instance.conditions)
condition_ids = []
for c in conditions_data.all():
condition_ids.append(c.id)
instance.conditions.set(condition_ids)
instance.save()
return instance