How can I apply a filter to a nested resource in Django REST framework?

Question

In my app I have the following models:

class Zone(models.Model):     name = models.SlugField()  class ZonePermission(models.Model):     zone = models.ForeignKey('Zone')     user = models.ForeignKey(User)     is_administrator = models.BooleanField()     is_active = models.BooleanField() 

I am using Django REST framework to create a resource that returns zone details plus a nested resource showing the authenticated user's permissions for that zone. The output should be something like this:

{     "name": "test",      "current_user_zone_permission": {         "is_administrator": true,          "is_active": true     } }  

I've created serializers like so:

class ZonePermissionSerializer(serializers.ModelSerializer):     class Meta:         model = ZonePermission         fields = ('is_administrator', 'is_active')  class ZoneSerializer(serializers.HyperlinkedModelSerializer):     current_user_zone_permission = ZonePermissionSerializer(source='zonepermission_set')      class Meta:         model = Zone         fields = ('name', 'current_user_zone_permission') 

The problem with this is that when I request a particular zone, the nested resource returns the ZonePermission records for all the users with permissions for that zone. Is there any way of applying a filter on request.user to the nested resource?

BTW I don't want to use a HyperlinkedIdentityField for this (to minimise http requests).

Solution

This is the solution I implemented based on the answer below. I added the following code to my serializer class:

current_user_zone_permission = serializers.SerializerMethodField('get_user_zone_permission')  def get_user_zone_permission(self, obj):     user = self.context['request'].user     zone_permission = ZonePermission.objects.get(zone=obj, user=user)     serializer = ZonePermissionSerializer(zone_permission)     return serializer.data 

Thanks very much for the solution!

Answer 1

I'm faced with the same scenario. The best solution that I've found is to use a SerializerMethodField and have that method query and return the desired values. You can have access to request.user in that method through self.context['request'].user.

Still, this seems like a bit of a hack. I'm fairly new to DRF, so maybe someone with more experience can chime in.