How to get a nested data structure, in Django Rest

Question

I'm working on a small project ( Kanban board ) using Django / Rest Framework, I have two models one for tasks and one another for status ( columns ), like ( started, pending, Done ).

everything works fine with me. the only issue I have is my data structure, is not correctly nested,

this is my models : (Status)

from django.db import models
from django.conf import settings
from contact.models import Contact

# Create your models here.

class Status(models.Model):
    title = models.CharField(blank=False, null=False, max_length=255)
    slug = models.CharField(blank=False, null=False, max_length=255)
    order = models.SmallIntegerField(default=0)

    def __str__(self):
        return self.title

This is my Task Model :

class Task(models.Model):

    status = models.ForeignKey(Status, on_delete=models.CASCADE, default=1)
    title = models.CharField(blank=False, max_length=255)

This is my serializer :

from rest_framework import serializers
from task.models import Task


class TaskSerializer(serializers.ModelSerializer):
    
    class Meta:
        model = Task
        fields = '__all__'
        depth = 1

The result that i get :

[
    {
        "id": 1,
        "title": "my task title must be inside status ",
        "status": {
            "id": 1,
            "title": "step1",
            "slug": "step1",
            "order": 1
        }
    }
]

**I would like to get a nested Data structure, my tasks my be inside the status dictionary, so I can loop ever the status and the tasks ( nested for loop )

score 0 · Accepted Answer · answered Apr 19 '21 at 23:01

Fixed this is the correct code :

from rest_framework import serializers
from task.models import Task, Status


class TaskSerializer(serializers.ModelSerializer):
    
    class Meta:
        model = Task
        fields = '__all__'



class StatusSerializer(serializers.ModelSerializer):
    tasks = TaskSerializer(many=True)
    class Meta:
        model = Status
        fields = '__all__'

This is the view:

def list(self, request):
        objectSerializer = StatusSerializer(Status.objects.all(), many=True)
        return Response(objectSerializer.data)

Víctor Villalobos · Answer 2 · 2021-04-19T22:46:00.960

-1

You need to create a StatusSerializer and inside this declare a field that uses your TaskSerializer defining many and source attributes, example:

from rest_framework import serializers
from task.models import Task, Status


class TaskSerializer(serializers.ModelSerializer):
    
    class Meta:
        model = Task
        fields = ("title", )
        depth = 1


class StatusSerializer(serializers.ModelSerializer):
    tasks = TaskSerializer(many=True, source="task_set")


    class Meta:
        model = Status
        fields = '__all__'
        depth = 1

Another way using a SerializerMethodField instead of a serializer:

class StatusSerializer(serializers.ModelSerializer):
    tasks = serializers.SerializerMethodField()

    def get_tasks(self, obj):
        queryset = Task.objects.filter(status=obj)
        return TaskSerializer(queryset, many=True).data
    
    class Meta:
        model = Status
        fields = '__all__'

https://www.django-rest-framework.org/api-guide/fields/#serializermethodfield

More About Inverse Relations in django:

Django What is reverse relationship?

edited Apr 19 '21 at 22:46

answered Apr 19 '21 at 18:49

Víctor Villalobos

69
2
9

can you explain to me the role of many + source please – Alice Munin Apr 19 '21 at 19:00
code doesn't work i get an error task_set doesn't exists as a field !!! – Alice Munin Apr 19 '21 at 19:09
what do you mean by task_set i cant find any documentation about – Alice Munin Apr 19 '21 at 19:10
any help please – Alice Munin Apr 19 '21 at 20:03
Hello, many: True, tells the serializer that's there will be many "Task" items. source: This specific the fields of the related model, in this case is the inverse relation from Status to Tasks, the default for this inverse relations is the name of the field underscore task, so, in this case you could do this query: `Status.task_set.all()` You could do this work using a SerializerMethodField too, I will add another example. – Víctor Villalobos Apr 19 '21 at 22:00
File "/root/project/task/api/serializers.py", line 13, in Meta model = Status NameError: name 'Status' is not defined – Alice Munin Apr 19 '21 at 22:07
can you juste organize one code for me if possible please – Alice Munin Apr 19 '21 at 22:11
your code give the same result, not the expected result – Alice Munin Apr 19 '21 at 22:27
Are you importing your models? my code is added to your base code, that error is because you are not importing your models in serializers.py – Víctor Villalobos Apr 19 '21 at 22:42
yes i did i fixed the bug, but the result, is not what i expected, your code give me the same result that i have :( – Alice Munin Apr 19 '21 at 22:43
can you please edit your code and write the view for me please – Alice Munin Apr 19 '21 at 22:44
Please add ".data" at the end the get_task method and test again, example: ```python def get_tasks(self, obj): queryset = Task.objects.filter(status=obj) return TaskSerializer(queryset, many=True).data ``` – Víctor Villalobos Apr 19 '21 at 22:46
what about the view, which serializer i should use ? Task or Status ? – Alice Munin Apr 19 '21 at 22:51
You should use the StatusSerializer. – Víctor Villalobos Apr 20 '21 at 00:57

How to get a nested data structure, in Django Rest

2 Answers2