nested one to many serializer model django - django

Question

I am trying to create a relationship between databases
result : =>
[
{
"id":1,
"title":"mobile",
"category_two":[
{
"id":3,
"title":"brand"
},
{
"id":4,
"title":"memory"
}
]
}
]
and i expect : =>
[
{
"id":1,
"title":"mobile",
"category_two":[
{
"id":3,
"title":"brand",
"category_three":[
{
"id":1,
"title":"samsung"
},
{
"id":2,
"title":"apple"
}
]
},
{
"id":4,
"title":"memory",
"category_three":[
{
"id":1,
"title":"32gb"
},
{
"id":2,
"title":"64gb"
}
]
}
]
}
]
// views
class get_Category(APIView):
def get(self, request):
category = CategoryOne.objects.all()
serializer = CategoryTwoSerializer(category, many=True)
return Response(serializer.data)
//serializers
class CategoryOneSerializer(serializers.ModelSerializer):
class Meta:
model = CategoryOne
fields = '__all__'
class CategoryTwoSerializer(serializers.ModelSerializer):
category_two= CategoryOneSerializer(many=True,read_only=True)
class Meta:
model = CategoryTwo
fields = '__all__'
depth=5
class CategoryThreeSerializer(serializers.ModelSerializer):
category_three = CategoryTwoSerializer(many=True,read_only=True)
class Meta:
model = CategoryThree
fields = '__all__'
depth=5
// models
class CategoryOne(models.Model):
title = models.CharField(max_length=225)
def __str__(self):
return self.title
class CategoryTwo(models.Model):
title = models.CharField(max_length=255)
categoryone = models.ForeignKey(CategoryOne,related_name='category_two',on_delete=models.SET_NULL,null=True)
def __str__(self):
return self.title
class CategoryThree(models.Model):
title = models.CharField(max_length=255)
categorytwo = models.ForeignKey(CategoryTwo,related_name='category_three',on_delete=models.SET_NULL,null=True)
def __str__(self):
return self.title

Answer 1

Try
class CategoryOneSerializer(serializers.ModelSerializer):
category_two= CategoryTwoSerializer(many=True,read_only=True)
class Meta:
model = CategoryOne
fields = '__all__'
class CategoryTwoSerializer(serializers.ModelSerializer):
category_three = CategoryThreeSerializer(many=True,read_only=True)
class Meta:
model = CategoryTwo
fields = '__all__'
class CategoryThreeSerializer(serializers.ModelSerializer):
class Meta:
model = CategoryThree
fields = '__all__'
// views
class get_Category(APIView):
def get(self, request):
category = CategoryOne.objects.prefetch_related("category_two", "category_two__category_three")
serializer = CategoryOneSerializer(category, many=True)
return Response(serializer.data)
If you want category_two rows related to a specific category_one to be serialized with it, you essentially want to add a non existing data to CategoryOne.
Since means you need two add it to the serializer and specify how to serialize it.
Here you can access this data by using a related_name, therefore adding a field with the proper related_name will suffice for django to find the data you want.
The same wan be done the serializer CategoryThree tied the a specific CategoryTwo row.
Howerver doing this will produce a LOT of SQL queries since each time my_category_on.category_two.all() is called by the serializer, an sql query is needed.
The prefetch_related() is here to solve the issue