How to serialize multiple relationship models in django rest framework

Question

I'm new to this Django rest framework and I'm trying to create an API. My model.py looks like the following

class FieldTypes(models.Model):
    field_type = models.CharField(max_length=255, null=False)
    deleted = models.BooleanField(default=False)

class Forms(models.Model):
    form_name = models.CharField(max_length=255, null=False)
    deleted = models.BooleanField(default=False)

class FormFields(models.Model):
    form = models.ForeignKey(Forms, related_name = 'form_fields', on_delete=models.CASCADE)
    field_type = models.ForeignKey(FieldTypes, related_name = 'form_field_types', on_delete=models.CASCADE)
    description = models.CharField(max_length=255, null=False)
    deleted = models.BooleanField(default=False)

class FormFieldOptions(models.Model):
    form_field = models.ForeignKey(FormFields, related_name = 'form_field_options', on_delete=models.CASCADE)
    description = models.CharField(max_length=255, null=False)
    deleted = models.BooleanField(default=False)

and the serializers.py looks like

class FormFieldSerializer(serializers.ModelSerializer):
    form_field_options = FormFieldOptionsSerializer(many=True)
    class Meta:
        model = FormFields
        fields = ('id', 'description', 'form_field_options')

class FormSerializer(serializers.ModelSerializer):
    form_fields = FormFieldSerializer(many=True)
    class Meta:
        model = Forms
        fields = ('form_name', 'form_fields')

class FieldTypeSerializer(serializers.ModelSerializer):
    class Meta:
        model = FieldTypes
        fields = ('field_type')

with that i was able to produce a result a like

{
    "form_name": "Ticket",
    "form_fields": [
        {
            "id": 1,
            "description": "Type",
            "form_field_options": [
                {
                    "id": 1,
                    "description": "Question"
                },
                {
                    "id": 2,
                    "description": "Incident"
                },
                {
                    "id": 3,
                    "description": "Problem"
                },
                {
                    "id": 4,
                    "description": "Task"
                }
            ]
        }
    ]
}

but i need to know which field type the form fields belongs to. And I'm not sure about how to bring field types in the JSON data. Kindly guide me to get the expected result. Please let me know if I Should reform the data models to get the expected result.

Traceback:

File "C:\Python\lib\site-packages\django\core\handlers\exception.py" in inner
  34.             response = get_response(request)

File "C:\Python\lib\site-packages\django\core\handlers\base.py" in _get_response
  126.                 response = self.process_exception_by_middleware(e, request)

File "C:\Python\lib\site-packages\django\core\handlers\base.py" in _get_response
  124.                 response = wrapped_callback(request, *callback_args, **callback_kwargs)

File "C:\Python\lib\site-packages\django\views\decorators\csrf.py" in wrapped_view
  54.         return view_func(*args, **kwargs)

File "C:\Python\lib\site-packages\rest_framework\viewsets.py" in view
  103.             return self.dispatch(request, *args, **kwargs)

File "C:\Python\lib\site-packages\rest_framework\views.py" in dispatch
  483.             response = self.handle_exception(exc)

File "C:\Python\lib\site-packages\rest_framework\views.py" in handle_exception
  443.             self.raise_uncaught_exception(exc)

File "C:\Python\lib\site-packages\rest_framework\views.py" in dispatch
  480.             response = handler(request, *args, **kwargs)

File "C:\Python\lib\site-packages\rest_framework\mixins.py" in list
  48.         return Response(serializer.data)

File "C:\Python\lib\site-packages\rest_framework\serializers.py" in data
  765.         ret = super(ListSerializer, self).data

File "C:\Python\lib\site-packages\rest_framework\serializers.py" in data
  262.                 self._data = self.to_representation(self.instance)

File "C:\Python\lib\site-packages\rest_framework\serializers.py" in to_representation
  683.             self.child.to_representation(item) for item in iterable

File "C:\Python\lib\site-packages\rest_framework\serializers.py" in <listcomp>
  683.             self.child.to_representation(item) for item in iterable

File "C:\Python\lib\site-packages\rest_framework\serializers.py" in to_representation
  527.                 ret[field.field_name] = field.to_representation(attribute)

File "C:\Python\lib\site-packages\rest_framework\serializers.py" in to_representation
  683.             self.child.to_representation(item) for item in iterable

File "C:\Python\lib\site-packages\rest_framework\serializers.py" in <listcomp>
  683.             self.child.to_representation(item) for item in iterable

File "C:\Python\lib\site-packages\rest_framework\serializers.py" in to_representation
  510.         fields = self._readable_fields

File "C:\Python\lib\site-packages\django\utils\functional.py" in __get__
  37.         res = instance.__dict__[self.name] = self.func(instance)

File "C:\Python\lib\site-packages\rest_framework\serializers.py" in _readable_fields
  376.             field for field in self.fields.values()

File "C:\Python\lib\site-packages\rest_framework\serializers.py" in fields
  363.             for key, value in self.get_fields().items():

File "C:\Python\lib\site-packages\rest_framework\serializers.py" in get_fields
  1045.                 source, info, model, depth

File "C:\Python\lib\site-packages\rest_framework\serializers.py" in build_field
  1190.         return self.build_unknown_field(field_name, model_class)

File "C:\Python\lib\site-packages\rest_framework\serializers.py" in build_unknown_field
  1302.             (field_name, model_class.__name__)

Exception Type: ImproperlyConfigured at /forms/
Exception Value: Field name `field_type` is not valid for model `FormFields`.

Answer 1

Add field_type field in FormFieldSerializer as

class FormFieldSerializer(serializers.ModelSerializer):
    form_field_options = FormFieldOptionsSerializer(many=True)
    class Meta:
        model = FormFields
        fields = ('id', 'description', 'form_field_options','field_type')

This will return the PK of FieldType instance.


If you want to show the string representation, use below snippet

class FormFieldSerializer(serializers.ModelSerializer):
    form_field_options = FormFieldOptionsSerializer(many=True)
    field_type = serializers.CharField(source='field_type.field_type')

    class Meta:
        model = FormFields
        fields = ('id', 'description', 'form_field_options', 'field_type')