How to extend model on serializer level with django-rest-framework

Question

My model looks like this:

class MenuItem(models.Model):
    name = models.CharField(max_length=500)
    components = models.ManyToManyField(Component, throug         


        

Answer 1

First, create a view that will return the MenuItemComponent instances that you're interested in.

class ListComponents(generics.ListAPIView):
    serializer_class = MenuItemComponentSerializer

    def get_queryset(self):
        """
        Override .get_queryset() to filter the items returned by the list.
        """
        menuitem = self.kwargs['menuitem']
        return MenuItemComponent.objects.filter(menuItem=menuitem)

Then you need to create a serializer to give you the representation you want. Your example is a bit more interesting/involved than the typical case, so it'd look something like this...

class MenuItemComponentSerializer(serializers.Serializer):
    url = ComponentURLField(source='component')
    name = Field(source='component.name')
    isReplaceable = Field()

The fields 'name' and 'isReplaceable' can simply use the default read-only Field class.

There's no field that quite meets your 'url' case here, so we'll create a custom field for that:

class ComponentURLField(serializers.Field):
    def to_native(self, obj):
        """
        Return a URL, given a component instance, 'obj'.
        """

        # Something like this...
        request = self.context['request']
        return reverse('component-detail', kwargs=kwargs, request=request)

I think that should all be about right.

That's for a read-only serialization - if you wanted a writable serialization you'd need to look into overriding the restore_object method on the serializer, and using WritableField, or something along those lines.