instance expected, got OrderedDict Django Rest Framework writable nested serializers - nested

Question

I am creating a survey kind of app, so i have three models Form, Questiosn, Choices[for multiple choice questions]
I followed this tutorial http://www.django-rest-framework.org/api-guide/relations/#nested-relationships
It works fine for 1 level nested relations, but for 2 levels it gives
TypeError: 'Choice' instance expected, got OrderedDict([(u'title', u'option1')])
class ChoiceSerializer(serializers.ModelSerializer):
class Meta:
model = Choice
fields = ['title']
class QuestionSerializer(serializers.ModelSerializer):
choices = ChoiceSerializer(many=True, required=False)
class Meta:
model = Question
fields = ['title', 'type', 'required','order','choices']
def create(self, validated_data):
choices_data = validated_data.pop("choices")
question = Question.objects.create(**validated_data)
for choice_data in choices_data:
Choice.objects.create(question=question, **choice_data)
return question
class FormSerializer(serializers.ModelSerializer):
questions = QuestionSerializer(many=True)
class Meta:
model = Form
fields = ['title', 'description', 'created', 'active', 'hash','questions']
read_only_fields = ['active','hash']
def create(self, validated_data):
questions_data = validated_data.pop('questions')
form = Form.objects.create(**validated_data)
for question_data in questions_data:
Question.objects.create(form=form, **question_data)
return form
EDIT
Solved using the manual way, In FormSerializer override the create method,
#transaction.atomic
def create(self, validated_data):
try:
with transaction.atomic():
questions_data = validated_data.pop('questions')
form = Form.objects.create(**validated_data)
for question_data in questions_data:
question = Question.objects.create(form=form,
title=question_data['title'],
type=question_data['type'],
required=question_data['required'])
if question.type == Question.RADIO or question.type == Question.CHECKBOX:
choices_data = question_data.pop('choices')
for choice_data in choices_data:
choice = Choice.objects.create(question=question, title=choice_data['title'])
return form
except Exception, e:
raise serializers.ValidationError("Cannot Save Form %s" % e)

Answer 1

I also struggled with this and I believe the proper way to handle this is:
class ChoiceSerializer(serializers.ModelSerializer):
class Meta:
model = Choice
fields = ['title']
class QuestionSerializer(serializers.ModelSerializer):
choices = ChoiceSerializer(many=True, required=False)
class Meta:
model = Question
fields = ['title', 'type', 'required','order','choices']
class FormSerializer(serializers.ModelSerializer):
questions = QuestionSerializer(many=True)
class Meta:
model = Form
fields = ['title', 'description', 'created', 'active',
'hash','questions']
read_only_fields = ['active','hash']
def create(self, validated_data):
questions_data = validated_data.pop('questions')
form = Form.objects.create(**validated_data)
for question_data in questions_data:
choices_data = question_data.pop('choices')
Question.objects.create(form=form, **question_data)
for choice_data in choices_data:
choice = Choice.objects.create(question=question, **choice_data)
return form
An easy way to screw this up is to not pop choices before creating the Question object. When you do that, you'll get an instance expected, got OrderedDict( 500 error.
Note also that you do not need to define create() on the QuestionSerializer. All child processing is done at the top level.