Graphene: Calculated fields

[sgtsquiggs]

How do we access calculated fields? In a serializer I would do something like

class ArtworkSerializer(serializers.ModelSerializer):
    url = serializers.URLField(source='get_absolute_url')

    class Meta:
        model = Artwork
        fields = ('id', 'title', 'url')

I assume I need to specify this somehow in class ArtworkNode(DjangoNode): but I've been unable to discover how.

[sgtsquiggs]

Figured it out.

class ArtworkNode(DjangoNode):
    url = graphene.String()

    class Meta:
        model = Artwork
        filter_fields = ['id', 'title']

    def resolve_url(self, args, info):
        return self.instance.url

Is it possible to retrieve via pk?

[syrusakbary]

Great! However I'm going to add the source option to fields! It makes it much more pleasant to develop!

So you can do something like

class ArtworkNode(DjangoNode):
    url = graphene.String(source='get_absolute_url')

    class Meta:
        model = Artwork
        filter_fields = ['id', 'title']

[syrusakbary]

@sgtsquiggs You can retrieve an Artwork Node doing:

{
  node(id:"SOME_STRING") {
    id
  }
}

In this case SOME_STRING will be the value of ArtworkNode.global_id(1).

[sgtsquiggs]

Is it possible to get a single item via a field other than id? for instance I have a slug field on Artwork and in my django endpoint I use Artwork.get_by_slug(slug).

source= would be perfect, I use it extensively in my serializers

[syrusakbary]

Sure. You can do it using arguments.

class Query(graphene.ObjectType):
    artwork = graphene.Field(ArtworkNode, slug=graphene.String())

    def resolve_artwork(self, args, info):
        return Artwork.get_by_slug(args.get('slug', None))

Then you can query it with the following query:

{
  artwork(slug:"my_slug") {
    id
    title
  }
}

Hope it helps!

[paymog]

How do I resolve a django object along with an extra, calculated field like below during a query?

class ProjectType(DjangoObjectType):
    class Meta:
        model = Project

    extra_field = graphene.String()


class Query(ObjectType):
    project = graphene.Field(ProjectType,
                             name=graphene.String())

    def resolve_project(self, info, name):

        if id is not None:
            return Project.objects.get(pk=id) # how do I populate `extra_field` here?


        return None