getting null in object of many to many relation object django-CodePudding

I'm saving an object with many to many relations in the database but when I'm fetching it so so it returns me IDs of that relational object but I want to the whole object instead, so I have added a property in the serializer and after that, it returns me the object.name only and the value of it is null, I don't know why it is behaving like this? anyone can help?

views.py

queryset = Tag.objects.filter(project_id=project_id).all()
serializer = TagSerializer(queryset, many=True)
return Response(serializer.data)

serializers.py

class TagSerializer(serializers.ModelSerializer):
    class Meta:
        model = Tag
        # fields = '__all__'
        fields = ['id', 'name', 'description', 'singleline']

    singleline = SinglelineSerializer(read_only=True)

models.py

class Tag(models.Model): 
    name = models.CharField(max_length=255, default='')
    description = models.CharField(max_length=255, default='')
    singleline = models.ManyToManyField(Singleline)
   
    class Meta:
        db_table = 'tags'

CodePudding user response：

A Tag can have many Singlelines, you need to work with many=True since it is a collection:

class TagSerializer(serializers.ModelSerializer):
    singleline = SinglelineSerializer(read_only=True, many=True)
    
    class Meta:
        model = Tag
        fields = ['id', 'name', 'description', 'singleline']

You can improve efficiency of the view by prefetcing the singleline relation and thus load all the related Singlelines in bulk:

queryset = Tag.objects.filter(project_id=project_id).prefetch_related('singleline')
serializer = TagSerializer(queryset, many=True)
return Response(serializer.data)