Django rest framework - filtering for serializer field
I have question about Django REST-full framework.
When products have rendered into remote client, each of product takes a filed with filtered data.
For example, model may be like this.
class Product(models.Model):
name = models.CharField()
class Like(models.Model):
product = models.ForeignKey(Product, related_name="likes")
On the client, each likes of product counted with true value, not false.
So I tried with below code in the serializer.
class ProductSerializer(serializers.ModelSerializer):
likes = serializers.PrimaryKeyRelatedField(many=True, queryset=Like.objects.filter(whether_like=True))
class Meta:
model = Product
fields = ('id', 'name', 'likes')
But, that is not working as I wanted.
What should I do?
The following is extra view code.
@api_view(['GET'])
def product_list(request, user_id, format=None):
if request.method == 'GET':
products = Product.objects.all()
serializer = ProductSerializer(products, many=True)
return Response(serializer.data)
Solution 1:
How about something like this:
class ProductSerializer(serializers.ModelSerializer):
likes = serializers.SerializerMethodField()
def get_likes(self, product):
qs = Like.objects.filter(whether_like=True, product=product)
serializer = LikeSerializer(instance=qs, many=True)
return serializer.data
class Meta:
model = Product
fields = ('id', 'name', 'likes')
**LikeSerializer
omitted for brevity. Hope this helps.
Solution 2:
Instead of SerializerMethodField
, which causes one additional database query per object, you can now (starting with Django 1.7) use Prefetch
objects in the queryset of your DRF ViewSet
:
from rest_framework import viewsets
from django.db.models import Prefetch
class ProductViewSet(viewsets.ModelViewSet):
queryset = Product.objects.prefetch_related(Prefetch(
'likes',
queryset=Like.objects.filter(like=True)))
The prefetch needs just one query, ensuring vastly superior performance compared to SerializerMethodField
.