Filtering against query parameters Django REST Framework, Many to Many

Question

I'm trying to build some kind of API, but I need to filtering request against query parameters in the URL (http:// ... / ?arg1=foo1&arg2=foo2&...). In my model scheme, I used a many to many relationships. Here is some of my code:

my_app/models.py

from django.contrib.postgres.fields import JSONField
from django.db import models


class MyData(models.Model):
    name = models.CharField(max_length=20)
    values = JSONField()


class MyModel(models.Model):
    time = models.DateTimeField()
    country = models.CharField(max_length=50)
    data = models.ManyToManyField(MyData)

my_app/serializers.py

from rest_framework import serializers
from my_app.models import MyModel, MyData


class MyDataSerializer(serializers.ModelSerializer):
    class Meta:
        model = MyData
        fields = ('name', 'values',)


class MyModelSerializer(serializers.ModelSerializer):
    data = MyDataSerializer(many=True, read_only=True)

    class Meta:
        model = MyModel
        fields = ('country', 'data',)

my_app/views.py

from rest_framework import generics
from my_app.serializers import MySerializer
from my_app.models import MyModel


class MyView(generics.ListAPIView):
    serializer_class = MySerializer

    def get_queryset(self):
        queryset = MyModel.objects.all()
        names = self.request.query_params.get('Simon', None)
        if names:
            queryset = queryset.filter(data__name__in=names.split(','))
        return queryset

and here are the responses

Response to http://127.0.0.1:8000/hello/

HTTP 200 OK
Allow: GET, HEAD, OPTIONS
Content-Type: application/json
Vary: Accept

[
    {
        "country": "Spain",
        "data": [
            {
                "name": "Mark",
                "values": {"A": "Hello, it's Wario"}
            },
            {
                "name": "Simon",
                "values": {"A": "Hello, it's Mario"}
            },
        ]
    },

    {
        "country": "Italy",
        "data": [
            {
                "name": "Jake",
                "values": {"A": "Hello, it's Luigi"}
            }
        ]
    }
]

Response to http://127.0.0.1:8000/hello/?name=Simon

HTTP 200 OK
Allow: GET, HEAD, OPTIONS
Content-Type: application/json
Vary: Accept

[
    {
        "country": "Spain",
        "data": [
            {
                "name": "Mark",
                "values": {"A": "Hello, it's Wario"}
            },
            {
                "name": "Simon",
                "values": {"A": "Hello, it's Mario"}
            },
        ]
    }
]

But the response I wanna to obtain when I request ?name=Simon is:

Response to http://127.0.0.1:8000/hello/?name=Simon

HTTP 200 OK
Allow: GET, HEAD, OPTIONS
Content-Type: application/json
Vary: Accept

[
    {
        "country": "Spain",
        "data": [
            {
                "name": "Simon",
                "values": {"A": "Hello, it's Mario"}
            }
        ]
    }
]

Community · Accepted Answer · 2020-06-20 09:12:55Z

I think we can do this with Django Filter package. To use this package you need to install it as any other python packages. pip install django-filter will do the same for you. Then you need to define a custom filter class anywhere in the project as down below,

from django_filters import rest_framework as filters
from my_app.models import MyModel

class MyFilter(filters.FilterSet):
    name = filters.CharFilter(name='data__name')

    class Meta:
        model = MyModel
        fields = ['name', ]

Then you have to change your views.py slightly as below,

from django_filters import rest_framework as filters


class MyView(generics.ListAPIView):
    serializer_class = MyModelSerializer
    filter_backends = (filters.DjangoFilterBackend,)
    filter_class = MyFilter

    def get_queryset(self):
        return MyModel.objects.all()

Note: I think you can define and use any kind of filter using this awesome package my customizing the filter class

neverwalkaloner · Accepted Answer · 2018-02-18 13:27:31Z

Try to use prefetch_related to filter related data:

from django.db.models import Prefetch

class MyView(generics.ListAPIView):
    serializer_class = MySerializer

    def get_queryset(self):
        queryset = MyModel.objects.all()
        names = self.request.query_params.get('Simon', None)
        if names:
            queryset = queryset.filter(data__name__in=names.split(',')).prefetch_related(Prefetch('data', queryset=MyData.objects.filter(name__in=names.split(',')))
        return queryset

Also you can use SerializerMethodField:

class MyModelSerializer(serializers.ModelSerializer):
    data = SerializerMethodField()

    class Meta:
        model = MyModel
        fields = ('country', 'data',)

    def get_data(self, obj):
        names = self.context['request'].query_params.get('Simon', None)
        data = MyData.objects.filter(name__in=names.split(','))
        data_serializer = MyDataSerializer(data, many=True)
        return data_serializer.data

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Filtering against query parameters Django REST Framework, Many to Many

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But the response I wanna to obtain when I request ?name=Simon is:

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