Develop Reference

Filter Embedded Document List in GraphQL

I'm building a GraphQL application in Python/Graphene using a MongoDB backend (through MongoEngine). Everything has been working well, but noticed that there's not a lot documentation for handling nested lists of embedded documents. I thought one power of GraphQL was the ability to project only the properties you want, but it doesn't appear to be the case fully.
Looking at this collection as an example:
[
{
"name": "John Doe",
"age": 37,
"preferences": [
{
"key": "colour",
"value": "Green"
},
{
"key": "smell",
"value": "onions cooking in butter"
},
...
]
},
...
]
If I want to find a particular object through GraphQL, I would look up through a query like
{
person(name: "John Doe"){edges{node{
name age preferences{edges{node{
key value
}}}
}}}
}
But this could bring back hundreds of nested documents. What I would like to do instead is to identify the requested nested documents as part of the projection request.
{
person(name: "John Doe"){edges{node{
name age preferences(key: "colour"){edges{node{
key value
}}}
}}}
}
My understanding reading the GraphQL spec is these sub-queries are not possible, but wanted to confirm with experts first. And if it is possible, how would I implement it to support these types of requests?
Update Maybe a schema example will provide some more insightful responses.
class PreferenceModel(mongoengine.EmbeddedDocument):
key = mongoengine.fields.StringField()
value = mongoengine.fields.StringField()
class Preference(graphene_mongo.MongoengineObjectType):
class Meta:
interfaces = (graphene.relay.Node, )
model = PreferenceModel
class PersonModel(mongoengine.Document):
meta = {'collection': 'persons'}
name = mongoengine.fields.StringField()
age = mongoengine.fields.IntField()
preferences = mongoengine.fields.EmbeddedDocumentListField(PreferenceModel)
class Person(graphene_mongo.MongoengineObjectType):
class Meta:
interfaces = (graphene.relay.Node, )
model = PersonModel
class Query(graphene.ObjectType):
person = graphene_mongo.MongoengineConnectionField(Person)
schema = graphene.Schema(query=Query, types=[Person])
app = starlette.graphql.GraphQLApp(schema=schema)
Using this above structure, what changes would be necessary to allow for queries/filters on nested objects?

I had a similiar issue but working graphene-django. I solved it using custom resolvers on the DjangoObjectType, like this:
import graphene
from graphene_django import DjangoObjectType
from .models import Question, Choice, SubChoice
class SubChoiceType(DjangoObjectType):
class Meta:
model = SubChoice
fields = "__all__"
class ChoiceType(DjangoObjectType):
sub_choices = graphene.List(SubChoiceType, search_sub_choices=graphene.String())
class Meta:
model = Choice
fields = ("id", "choice_text", "question")
def resolve_sub_choices(self, info, search_sub_choices=None):
if search_sub_choices:
return self.subchoice_set.filter(sub_choice_text__icontains=search_sub_choices)
return self.subchoice_set.all()
class QuestionType(DjangoObjectType):
choices = graphene.List(ChoiceType, search_choices=graphene.String())
class Meta:
model = Question
fields = ("id", "question_text")
def resolve_choices(self, info, search_choices=None):
if search_choices:
return self.choice_set.filter(choice_text__icontains=search_choices)
return self.choice_set.all()
class Query(graphene.ObjectType):
all_questions = graphene.List(QuestionType, search_text=graphene.String())
all_choices = graphene.List(ChoiceType, search_text=graphene.String())
all_sub_choices = graphene.List(SubChoiceType)
def resolve_all_questions(self, info, search_text=None):
qs = Question.objects.all()
if search_text:
qs = qs.filter(question_text__icontains=search_text)
return qs
def resolve_all_choices(self, info, search_text=None):
qs = Choice.objects.all()
if search_text:
qs = qs.filter(choice_text__icontains=search_text)
return qs
def resolve_all_sub_choices(self, info):
qs = SubChoice.objects.all()
return qs
schema = graphene.Schema(query=Query)
you can find the example here: https://github.com/allangz/graphene_subfilters/blob/main/mock_site/polls/schema.py
It may work for you

Django Rest Framework, updating multiple objects in one

I am trying to update multiple objects using PATCH to my Django backend. This is the request I am sending:
[
{
"pk":78,
"weekday":1,
"from_hour":"21:00",
"to_hour":"12:00:00",
"closed":false,
"lunch":true,
"lunch_start":null,
"lunch_end":null,
"lunch2":false,
"lunch_start2":null,
"lunch_end2":null,
"appointment_interval":15,
"num_appointments_interval":4,
"office":79
},
{
"pk":79,
"weekday":2,
"from_hour":"09:00:00",
"to_hour":"12:00:00",
"closed":false,
"lunch":true,
"lunch_start":null,
"lunch_end":null,
"lunch2":false,
"lunch_start2":null,
"lunch_end2":null,
"appointment_interval":15,
"num_appointments_interval":4,
"office":79
},
{
"pk":80,
"weekday":3,
"from_hour":"09:00:00",
"to_hour":"12:00:00",
"closed":false,
"lunch":true,
"lunch_start":null,
"lunch_end":null,
"lunch2":false,
"lunch_start2":null,
"lunch_end2":null,
"appointment_interval":15,
"num_appointments_interval":4,
"office":79
},
{
"pk":81,
"weekday":4,
"from_hour":"09:00:00",
"to_hour":"12:00:00",
"closed":false,
"lunch":false,
"lunch_start":"14:59:50",
"lunch_end":"14:59:51",
"lunch2":false,
"lunch_start2":null,
"lunch_end2":null,
"appointment_interval":15,
"num_appointments_interval":4,
"office":79
},
]
I send this to a custom view where I am trying to serialize and update the data.
#api_view(['PATCH'])
#parser_classes((JSONParser,))
def updateOfficeHours(request):
office_id = request.data[0]['office']
qs = OfficeHour.objects.filter(office__pk=office_id)
office_hours = OfficeHoursSerializer(qs, data=request.data, many=True, partial=True)
if not office_hours.is_valid():
print(":(")
return Response(status=status.HTTP_500_INTERNAL_SERVER_ERROR)
else:
office_hours.save()
return Response(status=status.HTTP_200_OK)
I only end up getting this error:
AttributeError: 'QuerySet' object has no attribute 'pk'
It seems like this error comes up when you are looking for one object, but I have many=True. What am I doing wrong?

ListSerializer can solve the problem. Here's how:
class OfficeHoursListSerializer(serializers.ListSerializer):
def update(self, instances, validated_data):
# here you can implement your own logic for updating objects
# this is just an example
result = []
for instance in instances:
for data in validated_data:
if data['id'] == instance.pk:
instance.some_field = data['some_field']
instance.save()
result.append(instance)
return result
Then you need to specify the ListSerializer in the OfficeHoursSerializer:
class OfficeHoursSerializer(serializers.ModelSerializer):
# It needs to identify elements in the list using their primary key,
# so use a writable field here, rather than the default which would be read-only.
id = serializers.IntegerField()
...
class Meta:
...
list_serializer_class = OfficeHoursListSerializer

DRF: Right way to use ListCreateAPIView with nested serializer

I make a page that lists all the existing vendors and modules that apply to each vendor. Here I need to change the status of modules (active or unactive), and if the module does not exist, but need to make it active then create it. It looks roughly like this.
Vendor1 module1/false module2/true module3/true .....
Vendor2 module1/false module2/true module3/true .....
.....
.....
models.py
class RfiParticipation(models.Model):
vendor = models.ForeignKey('Vendors', models.DO_NOTHING, related_name='to_vendor')
m = models.ForeignKey('Modules', models.DO_NOTHING, related_name='to_modules')
active = models.BooleanField(default=False)
user_id = models.IntegerField()
rfi = models.ForeignKey('Rfis', models.DO_NOTHING, related_name='to_rfi', blank=True, null=True)
timestamp = models.DateTimeField(auto_now=True)
To display it, I use ListCreateAPIView() class and nested serializer
serializer.py
class VendorModulesListManagementSerializer(serializers.ModelSerializer):
to_vendor = RfiParticipationSerializer(many=True)
class Meta:
model = Vendors
fields = ('vendorid', 'vendor_name', 'to_vendor',)
read_only_fields = ('vendorid', 'vendor_name', )
def create(self, validated_data):
validated_data = validated_data.pop('to_vendor')
for validated_data in validated_data:
module, created = RfiParticipation.objects.update_or_create(
rfi=validated_data.get('rfi', None),
vendor=validated_data.get('vendor', None),
m=validated_data.get('m', None),
defaults={'active': validated_data.get('active', False)})
return module
class RfiParticipationSerializer(serializers.ModelSerializer):
class Meta:
model = RfiParticipation
fields = ('pk', 'active', 'm', 'rfi', 'vendor', 'timestamp')
read_only_fields = ('timestamp', )
views.py
class AssociateModulesWithVendorView(generics.ListCreateAPIView):
"""
RFI: List of vendors with participated modules and modules status
"""
permission_classes = [permissions.AllowAny, ]
serializer_class = VendorModulesListManagementSerializer
queryset = Vendors.objects.all()
I have a question about using the create serializer method when sending a POST request.
Now the input format looks like this
{
"to_vendor": [
{
"active": false,
"m": 1,
"rfi": "20R1",
"vendor": 15
}]
}
I.e. the dictionary key for the current code implementation is the list of one dictionary. If I remove " [] " from dict value I got
{
"to_vendor": {
"non_field_errors": [
"Expected a list of items but got type \"dict\"."
]
}
}
And this is the reason why I need to add a for loop in the create method to iterate through the list with just one element. I already have any doubts that I'm doing the right thing. Maybe I chose the wrong implementation way?
But now question is why do I get a mistake?
AttributeError: Got AttributeError when attempting to get a value for field `to_vendor` on serializer `VendorModulesListManagementSerializer`.
The serializer field might be named incorrectly and not match any attribute or key on the `RfiParticipation` instance.
Original exception text was: 'RfiParticipation' object has no attribute 'to_vendor'.
I would be very grateful for your help and advice!
upd
Get request format data:
[
{
"vendorid": 15,
"vendor_name": "Forest Gamp",
"to_vendor": [
{
"pk": 35,
"active": true,
"m": "Sourcing",
"rfi": "1",
"vendor": 15,
"timestamp": "2020-03-29T08:15:41.638427"
},
{
"pk": 39,
"active": false,
"m": "CLM",
"rfi": "20R1",
"vendor": 15,
"timestamp": "2020-03-29T09:09:03.431111"
}
]
},
{
"vendorid": 16,
"vendor_name": "Test21fd2",
"to_vendor": [
{
"pk": 41,
"active": false,
"m": "SA",
"rfi": "20R1",
"vendor": 16,
"timestamp": "2020-03-30T11:05:16.106412"
},
{
"pk": 40,
"active": false,
"m": "CLM",
"rfi": "20R1",
"vendor": 16,
"timestamp": "2020-03-30T10:40:52.799763"
}
]
}
]

It tries to access to_vendor on your model RfiParticipation and it complains that this property does not exist. related_name refers to the back relation on your Vendors model. So that you can do something like Vendors.to_vendor.all() and fetch all the RfiParticipation instances.
This happens when it tries to validate your input data, so even before it gets to the create function of your serializer.
If you are trying to create new RfiParticipation, why would you use a view that defines queryset = Vendors.objects.all()?
Instead define a view that takes care of creating RfiParticipation, since it seems that you already have a reference to Vendors. If I understand correctly, what you are trying to do is basically batch create RfiParticipation, so make a view that points to these.

I have gone through your implementation, and I suppose you might have used wrong generics class inheritance in views.py.
You should try to replace
class AssociateModulesWithVendorView(generics.ListCreateAPIView):
permission_classes = [permissions.AllowAny, ]
serializer_class = VendorModulesListManagementSerializer
queryset = Vendors.objects.all()
With
class AssociateModulesWithVendorView(generics.CreateAPIView, generics.ListAPIView):
permission_classes = [permissions.AllowAny, ]
serializer_class = VendorModulesListManagementSerializer
queryset = Vendors.objects.all()
You can check below links for reference:
CreateAPIView : https://www.django-rest-framework.org/api-guide/generic-views/#createmodelmixin
ListCreateAPIView : https://www.django-rest-framework.org/api-guide/generic-views/#listcreateapiview

Django Rest Framework receive primary key value in POST and return model object as nested serializer

I'm not completely sure that the title of my question is as specific as I wanted it to be, but this is the case:
I have a HyperlinkedModelSerializer that looks like this:
class ParentArrivalSerializer(serializers.HyperlinkedModelSerializer):
carpool = SchoolBuildingCarpoolSerializer()
class Meta:
model = ParentArrival
As you can see the carpool is defined as a nested serializer object and what I want is to be able to make a POST request to create a ParentArrival in this way (data as application/json):
{
...
"carpool": "http://localhost:8000/api/school-building-carpools/10/"
...
}
And receive the data in this way:
{
"carpool": {
"url": "http://localhost:8000/api/school-building-carpools/10/"
"name": "Name of the carpool",
...
}
}
Basically, I'm looking for a way to deal with nested serializers without having to send data as an object (but id or url in this case) in POST request, but receiving the object as nested in the serialized response.

I have been happy with my previous solution, but decided to look again and I think I have another solution that does exactly what you want.
Basically, you need to create your own custom field, and just overwrite the to_representation method:
class CarpoolField(serializers.PrimaryKeyRelatedField):
def to_representation(self, value):
pk = super(CarpoolField, self).to_representation(value)
try:
item = ParentArrival.objects.get(pk=pk)
serializer = CarpoolSerializer(item)
return serializer.data
except ParentArrival.DoesNotExist:
return None
def get_choices(self, cutoff=None):
queryset = self.get_queryset()
if queryset is None:
return {}
return OrderedDict([(item.id, str(item)) for item in queryset])
class ParentArrivalSerializer(serializers.HyperlinkedModelSerializer):
carpool = CarpoolField(queryset=Carpool.objects.all())
class Meta:
model = ParentArrival
This will allow you to post with
{
"carpool": 10
}
and get:
{
"carpool": {
"url": "http://localhost:8000/api/school-building-carpools/10/"
"name": "Name of the carpool",
...
}
}

It's simple.
As you know, Django appends "_id" to the field name in the ModelClass, and you can achieve it in the SerializerClass, and the original filed can also be achieved. All you have to do is like this
class ParentArrivalSerializer(serializers.HyperlinkedModelSerializer):
# ...
carpool_id = serializers.IntegerField(write_only=True)
carpool = SchoolBuildingCarpoolSerializer(read_only=True)
# ...
class Meta:
fields = ('carpool_id', 'carpool', ...)
And use carpool_id in POST request.

How about overriding the to_representation method?
class YourSerializer(serializers.ModelSerializer):
class Meta:
model = ModelClass
fields = ["id", "foreignkey"]
def to_representation(self, instance):
data = super(YourSerializer, self).to_representation(instance)
data['foreignkey'] = YourNestedSerializer(instance.foreignkey).data
return data

One way to do it is to keep 'carpool' as the default you get from DRF, and then add a read-only field for the nested object.
Something like this (I don't have time to test the code, so consider this pseudo-code. If you cannot get it to work, let me know, and will spend more time):
class ParentArrivalSerializer(serializers.HyperlinkedModelSerializer):
carpool_info = serializers.SerializerMethodField(read_only=True)
class Meta:
model = ParentArrival
fields = ('id', 'carpool', 'carpool_info',)
def get_carpool_info(self, obj):
carpool = obj.carpool
serializer = SchoolBuildingCarpoolSerializer(carpool)
return serializer.data
If your only nested object is carpool, I would also suggest switching to the regular ModelSerializer so carpool only shows the ID (10) and the nested object then can show the URL.
class ParentArrivalSerializer(serializers.ModelSerializer):
....
and then if it all works, you will be able to do a post with
{
"carpool": 10
}
and your get:
{
"carpool": 10
"carpool_info": {
"url": "http://localhost:8000/api/school-building-carpools/10/"
"name": "Name of the carpool",
...
}
}
I have never found another solution, so this is the trick I have used several times.

How can one customize Django Rest Framework serializers output?

I have a Django model that is like this:
class WindowsMacAddress(models.Model):
address = models.TextField(unique=True)
mapping = models.ForeignKey('imaging.WindowsMapping', related_name='macAddresses')
And two serializers, defined as:
class WindowsFlatMacAddressSerializer(serializers.Serializer):
address = serializers.Field()
class WindowsCompleteMappingSerializer(serializers.Serializer):
id = serializers.Field()
macAddresses = WindowsFlatMacAddressSerializer(many=True)
clientId = serializers.Field()
When accessing the serializer over a view, I get the following output:
[
{
"id": 1,
"macAddresses": [
{
"address": "aa:aa:aa:aa:aa:aa"
},
{
"address": "bb:bb:bb:bb:bb:bb"
}
],
"clientId": null
}
]
Almost good, except that I'd prefer to have:
[
{
"id": 1,
"macAddresses": [
"aa:aa:aa:aa:aa:aa",
"bb:bb:bb:bb:bb:bb"
],
"clientId": null
}
]
How can I achieve that ?

Create a custom serializer field and implement to_native so that it returns the list you want.
If you use the source="*" technique then something like this might work:
class CustomField(Field):
def to_native(self, obj):
return obj.macAddresses.all()
I hope that helps.
Update for djangorestframework>=3.9.1
According to documentation, now you need override either one or both of the to_representation() and to_internal_value() methods. Example
class CustomField(Field):
def to_representation(self, value)
return {'id': value.id, 'name': value.name}

Carlton's answer will work do the job just fine. There's also a couple of other approaches you could take.
You can also use SlugRelatedField, which represents the relationship, using a given field on the target.
So for example...
class WindowsCompleteMappingSerializer(serializers.Serializer):
id = serializers.Field()
macAddresses = serializers.SlugRelatedField(slug_field='address', many=True, read_only=True)
clientId = serializers.Field()
Alternatively, if the __str__ of the WindowsMacAddress simply displays the address, then you could simply use RelatedField, which is a basic read-only field that will give you a simple string representation of the relationship target.
# models.py
class WindowsMacAddress(models.Model):
address = models.TextField(unique=True)
mapping = models.ForeignKey('imaging.WindowsMapping', related_name='macAddresses')
def __str__(self):
return self.address
# serializers.py
class WindowsCompleteMappingSerializer(serializers.Serializer):
id = serializers.Field()
macAddresses = serializers.RelatedField(many=True)
clientId = serializers.Field()
Take a look through the documentation on serializer fields to get a better idea of the various ways you can represent relationships in your API.