Access different serializer if a queryset is empty Django Rest Framework

Question

I don't think I am implementing this correctly, but I am trying to change the serializer used for a queryset based on a condition (if there are no venues in one queryset, switch to another serializer and just return list object). I'm not quite sure how to do this.

Here is the view

class SavedVenuesViewSet(viewsets.ModelViewSet):
    serializer_class = UserVenueSerializer
    
    def get_queryset(self):
        list_id = self.request.GET.get('list_id', None)
        user = self.request.user.id
        print(user)
        print(list_id)
        print(type(list_id))
        qs = UserVenue.objects.filter(user_list=int(float(list_id)))
        if not qs:    
            print("EMPTY LIST") #this is where i try to switch serializer
            serializer_class = UserListSerializer
            return UserVenue.objects.filter(id=int(float(list_id)))
        else:
            return qs

Here are the relevant serializers:

class UserVenueSerializer(serializers.ModelSerializer):
    venue = mapCafesSerializer()
    
    class Meta:
        model = UserVenue
        fields = ['user', 'user_list', 'venue']
        depth = 2 

[...]

class UserListSerializer(serializers.ModelSerializer): 
    class Meta:
        model = UserList
        fields = ['id', 'user', 'list_name']
        depth = 2

The traceback isn't throwing an error but it isn't doing what I am hoping:

1
45
<class 'str'>
EMPTY LIST
[29/Sep/2021 11:05:36] "GET /api/savedvenues/?list_id=45 HTTP/1.1" 200 2

Amir Afianian · Accepted Answer · 2021-09-29 14:10:33Z

1

This is the correct practice to change serializer class in ModelViewSet:

You have to override get_serializesr_class method:

class SavedVenuesViewSet(viewsets.ModelViewSet):
    serializer_class = UserVenueSerializer
    
    def get_serializer_class(self):
        if not self.get_queryset():  # Check your conditions here
            return UserListSerializer
        else:
            return UserVenueSerializer

answered Sep 29, 2021 at 14:10

Amir Afianian

2,8274 gold badges27 silver badges49 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

André Henrique Mendes · Accepted Answer · 2021-09-29 13:49:54Z

0

You could remove serializer_class field from your view, and create get_serializer_class() method, that will contain the logic for choosing the serializer. Is the best practice.

But, you can also, do it in your get queryset.

First, remove serializer_class attribute from your view. Instead, set it inside your get_queryset method (with this.serializer_class);

def get_queryset(self):
    list_id = self.request.GET.get('list_id', None)
    qs = UserVenue.objects.filter(user_list=int(float(list_id)))
    if not qs:
        self.serializer_class = UserVenueSerializer  
        return UserVenue.objects.filter(id=int(float(list_id)))
    else:
        self.serializer_class = UserListSerializer
        return qs

Don't forget use the self.serializer_class.

edited Sep 29, 2021 at 13:49

answered Sep 29, 2021 at 11:31

André Henrique Mendes

6077 silver badges12 bronze badges

2 Comments

Klim Bim Over a year ago

Instead of this use self. this is java stuff

André Henrique Mendes Over a year ago

Sure, you're right... it's force of habit

Collectives™ on Stack Overflow

Access different serializer if a queryset is empty Django Rest Framework

2 Answers 2

Comments

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related