Django nested serializer with serializermethodfield

Question

Context

I have an API endpoint api/v1/checkin/ that returns the current DeviceGroup and the AppVersions for an App that have to be active.

Problem

The endpoint currently returns data along with the correctly filtered AppVersions like this:

{
    "customer_device_uuid": "8d252b78-6785-42ea-9aee-b6f9e0f870b5",
    "device_group": {
        "group_uuid": "869b409d-f281-492e-bb62-d3168aea4394",
        "device_group_name": "Default",
        "color": "#0a2f45",
        "is_default": true,
        "app_versions": [
            "2.0",
            "1.1"
        ]
    }
}

Goal

I want the app_versions in the response to contain more data like this:

{
    "customer_device_uuid": "8d252b78-6785-42ea-9aee-b6f9e0f870b5",
    "device_group": {
        "group_uuid": "869b409d-f281-492e-bb62-d3168aea4394",
        "device_group_name": "Default",
        "color": "#0a2f45",
        "is_default": true,
        "app_versions": [
            {
                "app_version_uuid": "UUID here",
                "app_version_name": "1.1",
                "package_id": "package name here",
                "auto_start": false,
                "version_code": 1,
                "version_name": "0.1",
                "source": "link to file here"
            }, ...
        ]
    }
}

Serializers

# serializers.py


class AppVersionSerializer(serializers.ModelSerializer):
    auto_start = serializers.BooleanField(source='app_uuid.auto_start')

    class Meta:
        model = AppVersion
        fields = ('app_version_uuid', 'app_version_name', 'package_id', 'auto_start', 'version_code', 'version_name',
                  'source')


class DeviceGroupSerializer(serializers.ModelSerializer):
    app_versions = serializers.SerializerMethodField(read_only=True)

    # filters the app versions per app
    def get_app_versions(self, model):
        qs = model.get_current_app_versions()
        return [o.app_version_name for o in qs]

    class Meta:
        model = DeviceGroup
        fields = ('group_uuid', 'device_group_name', 'color', 'is_default', 'app_versions')


class CheckinSerializer(serializers.ModelSerializer):
    device_group = DeviceGroupSerializer(many=False, read_only=True, source='group_uuid')

    class Meta:
        model = CustomerDevice
        fields = ('customer_device_uuid', 'customer_uuid', 'device_id_android', 'device_group')
        extra_kwargs = {
        'customer_uuid': {'write_only': True},
        'device_id_android': {'write_only': True}
    }

I am guessing that I have to change the get_app_versions() in order to achieve my goal but I have no idea how.

What should I change in order to get the response I want?

EDIT

The get_current_app_versions method that does the filtering

# models.py

def get_current_app_versions(self):
    return (
        AppVersion.objects
        .filter(appversiondevicegrouplink__release_date__lt=timezone.now())
        .filter(appversiondevicegrouplink__device_group=self)
        .order_by('app_uuid__app_uuid', '-appversiondevicegrouplink__release_date')
        .distinct('app_uuid__app_uuid')
    )

Incognos · Accepted Answer · 2019-05-06 12:00:16Z

1

You are correct in assuming that you will have to change get_app_versions and instead of returning a list in the line return [o.app_version_name for o in qs] you will need to return a list of dictionaries.

You will need to create a full serializer for the AppVersions model. and then in your get_app_versions properly serialize you return values by passing them into your new serializer which contains all the fields you would like to return return AppVersionSerializer2(qs, many=True).data.

You may have to override serialization of certain fields as they may not be handled well by the serializer automatically.

edited May 6, 2019 at 12:00

answered May 6, 2019 at 11:40

Incognos

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2 Comments

Stevy Over a year ago

Thanks for your reply. The qs returns an AppVersion object and results in a TypeError. I updatet my question and added the get_app_versions method.

Incognos Over a year ago

you need to serialize the qs that is being returned. One of the fields cannot be serialized, which is likely why you are getting a TypeError - can you posyt the full model as well?

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Django nested serializer with serializermethodfield

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