Nested JSON output for Primary and Foreign key Django Rest Framework

Question

Iam using Django 3.2 with Restframework. I have a Model as a for a Primary key named Tag and a Model connected as a foreign key named TagItem.

I tried to get a nested JSON output for it but its not working as expected.

Models.py

class Tags(models.Model):
    tagId = models.CharField(primary_key=True, max_length=100,default=1)
    section = models.CharField(max_length=100)
class TagItem(models.Model):
    tagId= models.ForeignKey(Tags, on_delete=models.CASCADE,default=1)
    select = models.BooleanField(default=False)
    name = models.CharField(max_length=50)

views.py

def get_tag_details(request):
    if request.method == 'GET':
        tag = Tags.objects.all()
        tagitem = TagItem.objects.all()

        TagSerializeobj = TagsSerializer(tag,many=True)
        TagItemSerializeobj = TagItemSerializer(tagitem, many=True)
        result = {}
        result['tag'] = TagSerializeobj.data
        for item in TagItemSerializeobj:
            if item.tagId == result['tag'].tagId:
                result['tagItem'] = item
        return Response(result)

Error: 'ListSerializer' object is not iterable How to iterate of get items nested under related Tags only.

Required output

{
      "id": 1,
      "section": "crafts",
      "items": [
        {
          "id": "10",
          "select": false,
          "name": "Wood"
        },
        {
          "id": "11",
          "select": false,
          "name": "Clay"
        }
    ]
},
   {
      "id": 2,
      "section": "states",
      "items": [
        {
          "id": "20",
          "select": false,
          "name": "Andhra Pradesh"
        },
        {
          "id": "21",
          "select": false,
          "name": "Arunachal Pradesh"
        },
    ]
}

Brian Destura · Accepted Answer · 2021-07-13 09:39:45Z

1

You don't need to do all those processing in your views. ModelSerializer can do it for you, so you can just define a model serializer for TagItem that is nested on a model serializer for Tag so something like:

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


class TagModelSerializer(serializers.ModelSerializer):
    items = serializers.SerializerMethodField()

    class Meta:
        model = Tag
        fields = '__all__'

    def get_items(self, obj):
        return TagItemModelSerializer(obj.tag_items.all(), many=True)

And in your views:

serializer = TagModelSerializer(Tags.objects.all(), many=True)
return Response(serializer.data)

edited Jul 13, 2021 at 9:39

answered Jul 13, 2021 at 7:25

Brian Destura

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6 Comments

Klim Bim Over a year ago

You can add depth = 1 at Meta instead of using serializers.SerializerMethodField()

Ankzious Over a year ago

Hi @bdbd, Gives a good path for nested serializers. But while implementing it give get_items() takes 1 positional argument but 2 were given. Should the function need no parameters?

Ankzious Over a year ago

Does this doc "django-rest-framework.org/api-guide/relations/…" be helpful? Or do you suggest some else?

Brian Destura Over a year ago

Edited. Forgot to use self so it should be: def get_items(self, obj):

Brian Destura Over a year ago

Also yes, thats the doc you can read to have more information about this.

|

nik · Accepted Answer · 2021-07-13 16:40:48Z

0

I get unexpected keyword error when i tried to assign

edited Jul 13, 2021 at 16:40

answered Jul 13, 2021 at 12:55

nik

11 bronze badge

1 Comment

Ankzious Over a year ago

Hi @Nik, With the error you shared, it looks like, the keyword passed during POST request is either incorrect or missing. Like "section" is entered as "sections" etc etc.

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