Django Restframework with nested json and custom key

Question

Iam using Django with Restframework. Iam trying to get a json output from serializers in a nested manner with key as one of the fields from model. I acheived the nested JSON but the json key for them is troubling me.

Here is my code and expected results out of it:

Models.py

class Tags(models.Model):
    tagId = models.CharField(primary_key=True, max_length=100, default=1)
    section = models.CharField(max_length=100,default=1)
    def __str__(self):
        return self.section

class TagItem(models.Model):
    section= models.ForeignKey(Tags, on_delete=models.CASCADE,default=1,related_name="items")
    select = models.BooleanField(default=False)
    name = models.CharField(max_length=50)
    def __str__(self):
        return self.name

serializers.py

class TagItemModelSerializer(serializers.ModelSerializer):
    class Meta:
        model = TagItem
        fields = '__all__'


class TagModelSerializer(serializers.ModelSerializer):
    items = TagItemModelSerializer(many=True)

    class Meta:
        model = Tags
        fields = ['pk','section', 'items']

Expected output:

 {
    "crafts" : {                //craft is comming from Tag model's "section"
        "id": 1,
        "section": "crafts",
        "items": [
          {
            "id": "10",
            "select": false,
            "name": "Wood",   
            "category": "crafts"   
          },

        ]
      },
    "states" : {
        "id": 2,
        "section": "states",
        "items": [
          {
            "id": "20",
            "select": false,
            "name": "Andhra Pradesh",
            "category": "states" 
          }
        ]
      },
      "others" : {
      "id": 3,
      "section": "others",
      "items": [
        {
          "id": "30",
          "select": false,
          "name": "Volunteer",
          "category": "others" 
        }
      ]
    }
}

Current output:

[                                           //cant get the key of Tag model's "section"
    {
        "pk": "1",
        "section": "states",
        "items": [
            {
                "id": 6,
                "select": false,
                "name": "Assam",
                "section": "1"
            }
        ]
    },
    {
        "pk": "2",
        "section": "others",
        "items": [
            {
                "id": 12,
                "select": false,
                "name": "Artisan",
                "section": "2"
            }
        ]
    },
    {
        "pk": "3",
        "section": "crafts",
        "items": [
            {
                "id": 9,
                "select": false,
                "name": "Metal",
                "section": "3"
            }
        ]
    }
]

Klim Bim · Accepted Answer · 2021-07-22 09:32:38Z

1

At your case, you would like to have a custom representation I think?

You can adjust it with overriding to_representation()

I provide two approaches:

serializer -> the better way but not quite the output you prefer

view

class TagModelView(views.APIView):

    def get(self, request):
        qs = Tags.objects.all()
        serializer = TagModelSerializer(qs, many=True)
        return Response(data=serializer.data)

serializer

class TagItemModelSerializer(serializers.ModelSerializer):
    category = serializers.SerializerMethodField()

    class Meta:
        model = TagItem
        fields = ['id', 'select', 'name', 'category']

    def get_category(self, instance):
        return instance.section.section


class TagModelSerializer(serializers.ModelSerializer):
    items = TagItemModelSerializer(many=True)

    class Meta:
        model = Tags
        fields = ['pk', 'section', 'items']

    def to_representation(self, instance):
        container = super().to_representation(instance)
        return {container.get('section'): container}

Making representation in your view -> output you would like to get

view

    def get(self, request):
        qs = Tags.objects.all()
        serializer = TagModelSerializer(qs, many=True)

        container = dict()
        for element in serializer.data:
            container.update(**element)

        return Response(data=container)

serializer

No change to my proposal obove.

update

I saw that your primary key of Tags is tagId and you are using fields = ['pk', 'section', 'items'] but you would like to have id as a key-name.

Relabeling can help you.

class TagModelSerializer(serializers.ModelSerializer):
    items = TagItemModelSerializer(many=True)
    id = serializers.CharField(source='tagId')

    class Meta:
        model = Tags
        fields = ['id', 'section', 'items']

edited Jul 22, 2021 at 9:32

answered Jul 22, 2021 at 9:10

Klim Bim

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4 Comments

Ankzious Over a year ago

Hi @Klim, Sorry for the late reply. I tried the above solution, and it worked quite well! Thanks a lot!

Ankzious Over a year ago

But on a curious case, how does this return instance.section.section worked? I mean section comes twice, what kind of sorcery was that? And I cant find this get_category, is this part of DRF?

Klim Bim Over a year ago

@Ankzious. 1. instance is one of many TagItem-objects because we wrote TagModelSerializer(qs, many=True) and qs is a QuerySet and the serializer iterates over it. get_<custom_name>(...) is a method that can do anything what you would like to display. At instance.section.section, instance is your current TagItem-object. .section is the fieldname of your ForeignKey in TagItem-model and the second .section is the fieldname of your CharField in Tags-model

Klim Bim Over a year ago

@Ankzious If you use get_<display_name>, DRF takes <display_name> as a key and uses it for displaying what your method is returning. It is a ´read_only´-field and cannot be used for saving/updating.

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Django Restframework with nested json and custom key

1 Answer 1

serializer -> the better way but not quite the output you prefer

view

serializer

Making representation in your view -> output you would like to get

view

serializer

update

4 Comments

Your Answer

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Collectives™ on Stack Overflow

1 Answer 1

serializer -> the better way but not quite the output you prefer

view

serializer

Making representation in your view -> output you would like to get

view

serializer

update

4 Comments

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