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

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"
        }
      ]
    },
 
  ]
}

can you add your desired JSON response example to the question so everyone can give you a good answer — Mahmoud Adel
– Mahmoud Adel, Commented Mar 20, 2021 at 21:59

Mahmoud Adel · Accepted Answer · 2024-01-31 10:56:28Z

2

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.Serializer):
    recents_count = serializers.SerializerMethodField()
    signed_count = serializers.SerializerMethodField()
    results = serializers.SerializerMethodField()

    def get_recents_count(self, obj):
        # I don't know what 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 in 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)

edited Jan 31, 2024 at 10:56

answered Mar 20, 2021 at 23:31

Mahmoud Adel

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3 Comments

Viktor Vostrikov Over a year ago

Thanks! Very good explanation. Somehow, I got only a single contract not the list of the contracts in my ContractResultSerializer, but I think I will solve it myself from now on! Also, by the way, can you look at my other question? stackoverflow.com/questions/66726368/…

Mahmoud Adel Over a year ago

Good to hear that. sorry for the late reply, I will check this other question now.

Amaury Le Roux Dupeyron Over a year ago

it's serializers.Serializer without the s

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