Django Rest Framework - HyperlinkedRelatedField for abstract base class - django-rest-framework

Question

My question is if is possible to add an HyperlinkedRelatedField in a serializer to get only the attributes of the base class. for example:
I want a json like that:
{
"modules": [
{
"moduleName": "M1: Fundamentos Técnicos",
"moduleDetails": "Bla bla bla.",
"moduleID": 0,
"userScore": 3,
"slides": [
{
"slideType": "Content",
"slideID": 0
},
{
"slideType": "Minigame1",
"slideID": 1
},
{
"slideType": "Video",
"slideID": 6
}
]
}
]
}
Here, Slide is the base class and Video and Minigame are subclasses.
Is possible this?, is possible add a HyperlinkedRelatedField for the url of each slide?.
Thanks in advance!
UPDATE!
this are my models:
class Module(TimeStampedModel):
moduleID = models.AutoField(primary_key=True)
moduleName = models.CharField(
max_length=100,
verbose_name='Nombre del modulo')
moduleDetails = models.TextField(verbose_name='Detalle')
moduleBullet1 = models.CharField(max_length=100, verbose_name='Punto 1')
moduleBullet2 = models.CharField(max_length=100, verbose_name='Punto 2')
moduleBullet3 = models.CharField(max_length=100, verbose_name='Punto 3')
moduleImageURL = models.ImageField(
upload_to="modulos", verbose_name='Imagen')
userScore = models.PositiveSmallIntegerField(
default=0, verbose_name='Score de usuario')
class Slide(TimeStampedModel):
CONTENT = 'Content'
MINIGAME = 'Minigame'
VIDEO = 'Video'
SLIDE_TYPE_CHOICES = (
(CONTENT, 'Contenido'),
(MINIGAME, 'Minigame'),
(VIDEO, 'Video'),
)
slideType = models.CharField(
max_length=20,
choices=SLIDE_TYPE_CHOICES,
default=CONTENT,
)
slideID = models.AutoField(primary_key=True)
slideOrder = models.PositiveSmallIntegerField(
verbose_name='Orden de visualizacion')
module = models.ForeignKey(Module, on_delete=models.CASCADE,
related_name="%(app_label)s_%(class)s_related",
related_query_name="%(app_label)s_%(class)ss",)
class Meta:
abstract = True
class VideoContent(Slide):
videoURL = models.URLField(verbose_name='URL de video')
class Minigame(Slide):
timeToFail=models.PositiveSmallIntegerField()
And in my serializers.py i want something like this:
class SlideSerializer(serializers.HyperlinkedModelSerializer):
class Meta:
model = Slide
fields = ('url', 'slideType', 'slideID')
class ModuleSerializer(serializers.ModelSerializer):
slides = SlideSerializer(many=True, read_only=True)
class Meta:
model = Module
fields = ('moduleID', 'moduleName', 'moduleDetails', 'moduleImageURL', 'userScore', 'slides')
My view.py
class ModuleViewSet(viewsets.ModelViewSet):
"""
This viewset automatically provides `list`, `create`, `retrieve`,
`update` and `destroy` actions.
"""
queryset = Module.objects.all()
serializer_class = ModuleSerializer
permission_classes = (permissions.IsAuthenticatedOrReadOnly,)
class SlideViewSet(viewsets.ModelViewSet):
"""
This viewset automatically provides `list`, `create`, `retrieve`,
`update` and `destroy` actions.
"""
queryset = Slide.objects.all()
serializer_class = SlideSerializer
permission_classes = (permissions.IsAuthenticatedOrReadOnly,)
Slide.Objects raise an error, AttributeError: type object 'Slide' has no attribute 'objects'

Answer 1

You can't query abstract base classes. Slice is an abstract class, you cannot use queryset = Slide.objects.all() in SlideViewSet because an abstract model isn't an actual database object, and therefore cannot be queried.
You have to choose between abstract inheritance, in which case there is no database relationship between the two classes, or multi-table inheritance, which keeps the database relationship at a cost of efficiency (an extra database join) for each query.
Using multi-table inheritance
class Slide(TimeStampedModel):
CONTENT = 'Content'
MINIGAME = 'Minigame'
VIDEO = 'Video'
SLIDE_TYPE_CHOICES = (
(CONTENT, 'Contenido'),
(MINIGAME, 'Minigame'),
(VIDEO, 'Video'),
)
slideType = models.CharField(
max_length=20,
choices=SLIDE_TYPE_CHOICES,
default=CONTENT,
)
slideID = models.AutoField(primary_key=True)
slideOrder = models.PositiveSmallIntegerField(
verbose_name='Orden de visualizacion')
module = models.ForeignKey(Module, on_delete=models.CASCADE,
related_name="%(app_label)s_%(class)s_related",
related_query_name="%(app_label)s_%(class)ss",)
class VideoContent(Slide):
videoURL = models.URLField(verbose_name='URL de video')
class Minigame(Slide):
timeToFail=models.PositiveSmallIntegerField()
Now, your viewset:
class SlideViewSet(viewsets.ModelViewSet):
"""
This viewset automatically provides `list`, `create`, `retrieve`,
`update` and `destroy` actions.
"""
queryset = Slide.objects.all()
serializer_class = SlideSerializer
permission_classes = (permissions.IsAuthenticatedOrReadOnly,)
Documentation on multi-table inheritance:
multi-table inheritance uses an implicit OneToOneField to link the
child and the parent, it’s possible to move from the parent down to
the child
Hope this clears the things up.