How to perform nested serialization in Django? - django

Question

I am new to Django.I am using Django REST Framework and I need to get json from serializers in the following format:
{
"result" : 200,
"categories" : [{
"id" : "V001",
"name": "Vehicles",
"description": "All types of motor and non-motor vehicles",
"icon": "http://images.maa.ae/static/icons/vehicles.png",
"subcategories": [{
"id" : "V00101",
"name": "Cars",
"description": "Motor Cars",
"subcategories": [{
"id" : "V0010101",
"name": "Passenger Cars",
"description": "All types of passenger cars"
}]
},
{
"id" : "V00102",
"name": "Bikes",
"description": "Bikes",
"subcategories": [{
"id" : "V0010201",
"name": "Motor Bikes",
"description": "All kinds of motor bikes"
},
{
"id" : "V0010202",
"name": "Sports Bikes",
"description": "All kinds of sports bikes"
}]
}]
}]
}
My Model class is:
class Category(models.Model):
_id = models.AutoField(primary_key=True)
name = models.CharField(max_length=128)
description = models.CharField(max_length=150,null=True, blank=True)
icon = models.ImageField(upload_to='icons',null=True, blank=True)
parent_id = models.ForeignKey('self', null=True, blank=True)
and my serializers class is:
class CategorySerializer(serializers.HyperlinkedModelSerializer):
class Meta:
model = Category
fields = ('_id', 'name', 'description', 'icon')
From above implementation I can get Array of Category objects in JSON format.
But I don't know how can I include 'subcategories' in my serializer class.Please help me to get an output similar to json shown in above format.

Answer 1

Use Django Rest Framework.
http://www.django-rest-framework.org/
Keep your code DRY
from rest_framework import serializers
class CategoriesSerializer(serializers.ModelSerializer):
class Meta:
model = Categories
Views
from rest_framework import viewsets
from .serializers import CategoriesSerializer
class CategoryViewSet(viewsets.ModelViewSet):
queryset = Categories.objects.all()
serializer_class = CategoriesSerializer
Example
models.py:
class Sprints(models.Model):
name = models.CharField(default='', blank=True, max_length=90)
description = models.TextField(default='')
class Tasks(models.Model):
date_posted = models.DateTimeField(auto_now_add=True)
name = models.CharField(default='', blank=True, max_length=90)
end = models.DateTimeField(null=True, blank=True)
sprint = models.ForeignKey(Sprints, related_name='tasks')
class Meta:
ordering = ['-date_posted']
unique_together = ['name', 'sprint']
serializers.py:
class TaskSerializer(serializers.ModelSerializer):
class Meta:
model = Tasks
fields = ('id', 'name', 'date_posted', 'end')
class SprintSerializer(serializers.ModelSerializer):
tasks = TaskSerializer(many=True, read_only=True)
class Meta:
model = Sprints
fields = ('id', 'name', 'description', 'tasks')
views.py
class SprintsViews(viewset.ModelViewSet):
queryset = Sprints.objects.all()
serializer_class = SprintSerializer
You can also add a slug field to the models to make them easier to deal with, but this is how for now :)

Answer 2

You should consider having a look at THIS. The usage of depth meta attribute enables you to retrieve related objects to the depth you set.
By doing so, it automatically retrieves nested data.
It is very convenient to avoid using serializers in both sides and thus having ImportError caused by cycles too.

Answer 3

Use related_name and on_delete on your parent_id field in models.py file
class Category(models.Model):
_id = models.AutoField(primary_key=True)
name = models.CharField(max_length=128)
description = models.CharField(max_length=150,null=True, blank=True)
icon = models.ImageField(upload_to='icons',null=True, blank=True)
parent_id = models.ForeignKey('self', null=True, blank=True, related_name='children', on_delete=models.CASCADE)
Now add the packege pip install djangorestframework-recursive on your project
serializers.py:
##################################
from rest_framework_recursive.fields import RecursiveField
##################################
class CategorySerializer(serializers.ModelSerializer):
children = RecursiveField(many=True)
class Meta:
model = Category
fields = ('_id', 'name', 'description', 'icon', 'parent_id', 'children')
views.py (Serializers view file):
class CategoryListAPIView(generics.ListAPIView):
serializer_class = CategorySerializer
queryset = Category.objects.filter(parent_id__isnull=True)
urls.py:
############################
############################
urlpatterns = [
path('category/', views.CategoryListAPIView.as_view(), name="categoryAPI"),
######################################
]