How to add additional fields, like count of objects to ModelSerializer with many=True - django

Question

I don't know how to add additional fields to my ModelSerializer, which accepts many=True. Here is all my code:
ViewSet:
def list(self, request, *args, **kwargs):
contracts = self.request.user.all_contracts
serializer = ContractGetSerializer(contracts, many=True, context={'request': request}, )
return Response({"results": serializer.data}, status=status.HTTP_200_OK)
ContractGetSerializer serializer. It also has inner Many=True fields
class ContractGetSerializer(serializers.ModelSerializer):
files = FileModelSerializer(many=True)
is_author = serializers.SerializerMethodField('is_author_method')
contract_signing_status = serializers.SerializerMethodField('get_recipient_signing_status')
def is_author_method(self, foo):
return foo.owner.id == self.context['request'].user.id
class Meta:
model = Contract
fields = ['id', 'is_author', 'title','contract_signing_status','files', ]
Now my ContractGetSerializer returns a ReturnList with all contracts. How can I add additional fields to that ReturnList and make it a dictionary?
I need for instance to return only 5 recent contracts (filtered by timestamp).
Also, I need to add total SIGNED contracts, and total PENDING contracts, counting all contracts data so that my frontend would not need to do this.
My current JSON:
{
"results": [
{
"id": 178,
"is_author": true,
"title": "ahhzhzh",
"message_to_all_recipients": null,
"contract_signing_status": "WAITING_FOR_ME",
"contract_signing_type": "SIMPLE",
"contract_signing_date": {
"start_date": "2010-09-04T14:15:22Z",
"end_date": "2010-09-04T14:15:22Z"
},
"recipients": [
{
"message": null,
"recipient_signing_status": "NOT_SIGNED",
"recipient_review_status": "NOT_REQUIRED",
"recipient_action": "SIGN",
"role": "ADMIN"
},
{
"message": null,
"recipient_signing_status": "NOT_SIGNED",
"recipient_review_status": "NOT_REQUIRED",
"recipient_action": "SIGN",
"role": "BASE"
}
]
},
{
"id": 179,
"is_author": true,
"title": "dhhdhd",
"message_to_all_recipients": null,
"contract_signing_status": "WAITING_FOR_ME",
"contract_signing_type": "SIMPLE",
"contract_signing_date": {
"start_date": "2010-09-04T14:15:22Z",
"end_date": "2010-09-04T14:15:22Z"
},
"recipients": [
{
"message": null,
"recipient_signing_status": "NOT_SIGNED",
"recipient_review_status": "NOT_REQUIRED",
"recipient_action": "SIGN",
"role": "ADMIN"
},
{
"message": null,
"recipient_signing_status": "NOT_SIGNED",
"recipient_review_status": "NOT_REQUIRED",
"recipient_action": "SIGN",
"role": "BASE"
}
]
},
]
}
My desired JSON:
{
"recents_count": 5,
"signed_count": 10,
"results": [
{
"id": 178,
"is_author": true,
"title": "ahhzhzh",
"message_to_all_recipients": null,
"contract_signing_status": "WAITING_FOR_ME",
"contract_signing_type": "SIMPLE",
"contract_signing_date": {
"start_date": "2010-09-04T14:15:22Z",
"end_date": "2010-09-04T14:15:22Z"
},
"recipients": [
{
"message": null,
"recipient_signing_status": "NOT_SIGNED",
"recipient_review_status": "NOT_REQUIRED",
"recipient_action": "SIGN",
"role": "ADMIN"
},
{
"message": null,
"recipient_signing_status": "NOT_SIGNED",
"recipient_review_status": "NOT_REQUIRED",
"recipient_action": "SIGN",
"role": "BASE"
}
]
},
{
"id": 179,
"is_author": true,
"title": "dhhdhd",
"message_to_all_recipients": null,
"contract_signing_status": "WAITING_FOR_ME",
"contract_signing_type": "SIMPLE",
"contract_signing_date": {
"start_date": "2010-09-04T14:15:22Z",
"end_date": "2010-09-04T14:15:22Z"
},
"recipients": [
{
"message": null,
"recipient_signing_status": "NOT_SIGNED",
"recipient_review_status": "NOT_REQUIRED",
"recipient_action": "SIGN",
"role": "ADMIN"
},
{
"message": null,
"recipient_signing_status": "NOT_SIGNED",
"recipient_review_status": "NOT_REQUIRED",
"recipient_action": "SIGN",
"role": "BASE"
}
]
},
]
}

Answer 1

There are multiple ways to do so, but I think doing this in serializers is better.
I will do something like this:
at view
def list(self, request, *args, **kwargs):
serializer = ContractResultSerializer(self.request.user, context={'request': request}, )
return Response(serializer.data, status=status.HTTP_200_OK)
at serializers
class ContractResultSerializer(serializers.Serializers):
recents_count = serializers.SerializerMethodField()
signed_count = serializers.SerializerMethodField()
results = serializers.SerializerMethodField()
def get_recents_count(self, obj):
# I don't know how is your model looks like to write the query to get the recent count
# but I think it will be something like this
return obj.contracts.filter(your recent condition).count()
def get_signed_count(self, obj):
# is the same as get_recents_count()
def get_results(self, obj):
return ContractGetSerializer(obj.all_contracts, many=True, context={'request': self.context['request']}).data
class ContractGetSerializer(serializers.ModelSerializer):
files = FileModelSerializer(many=True)
is_author = serializers.SerializerMethodField('is_author_method')
contract_signing_status = serializers.SerializerMethodField('get_recipient_signing_status')
def is_author_method(self, foo):
return foo.owner.id == self.context['request'].user.id
class Meta:
model = Contract
fields = ['id', 'is_author', 'title','contract_signing_status','files', ]
You can also do the same if you like at your view instead of writing a new serializer
for ex:
def list(self, request, *args, **kwargs):
contracts = self.request.user.all_contracts
serializer = ContractGetSerializer(contracts, many=True, context={'request': request}, )
response ={
"recents_count": self.request.user.contracts.filter(your recent condition).count(),
"signed_count": self.request.user.contracts.filter(your recent condition).count(),
"results": serializer.data
}
return Response(response, status=status.HTTP_200_OK)