How to iterate ManyToMany filed in serializer class - django

Question

I have this Event model:
# models.py
class Event(models.Model):
name = models.CharField(max_length=200))
user = models.ManyToManyField(User))
This is my ListCreateAPIView class:
class EventListView(LoginRequiredMixin, generic.ListView):
model = Event
This is my ListCreateAPIView class:
class Events(generics.ListCreateAPIView):
permission_classes = (IsAuthenticated,)
queryset = Event.objects.all()
serializer_class = EventSerializer
This is my serialiser class:
#serializers,py
class EventSerializer(serializers.ModelSerializer):
class Meta:
fields = (
‘id',
'name',
'user',
)
model = Event
And this is my REST request response:
{
"count": 2,
"next": null,
"previous": null,
"results": [
{
"id": 1,
"name": "My event1",
"user": [
1,
4
],
"registered": true // <—- I NEED THIS
},
{
"id": 2,
"name": "Other event",
"user": [
2,
4,
6
],
"registered": false // <—- I NEED THIS
}
]
}
What I am gonna need in REST response is property “registered”, which will contain true or false if current user is registered on particular event or not.
My approach was to control if current user is in list of users of event. I tried to get this information in serialiser class this way:
#serializers,py
class EventSerializer(serializers.ModelSerializer):
registered = serializers.SerializerMethodField(‘_user’)
def _user(self, obj):
request = getattr(self.context, 'request', None)
if request.user in self.user:
return True
else:
return False
class Meta:
fields = (
‘id',
'name',
'user',
)
model = Event
But I get AttributeError: 'NoneType' object has no attribute 'user'
How can I solve this problem?

Answer 1

You can try like this using exists() with filter method:
class EventSerializer(serializers.ModelSerializer):
registered = serializers.SerializerMethodField(‘_user’)
def _user(self, obj):
request = self.context.get('request', None)
if request and obj.user.filter(pk=request.user.pk).exists():
return True
else:
return False

Answer 2

In view.py add
For This "registered": true // <—- I NEED THIS
model_name.object.filter(column='required value')