GenericRelations

I’ve been reading through the source code and the docs and I’ve been trying to get a GenericRelation to work, but I can’t work it out. I feel like there’s some cleverness to be done with a resolve method. Any tips?

# ignoring imports

class TaggedItem(models.Model):
    tag = models.SlugField()
    content_type = models.ForeignKey(ContentType, on_delete=models.CASCADE)
    object_id = models.PositiveIntegerField()
    content_object = GenericForeignKey('content_type', 'object_id')  # does not resolve

class Bookmark(models.Model):
    url = models.URLField()
    tags = GenericRelation(TaggedItem)  # is not automatically available

class TaggedItemNode(graphene_django.types.DjangoObjectType):
    # parent = graphene.ID() ... ?

    # resolve_parent(...) ... ?

    class Meta:
        model = TaggedItem
        interfaces = (graphene.Node,)

class BookmarkNode(graphene_django.types.DjangoObjectType):
    # tags = graphene.ID()  ... ?

    # resolve_tags(...) ... ?

    class Meta:
        model = Bookmark
        interfaces = (graphene.Node,)

Any help much appreciated.

P

[jameswyse]

I’m using GenericRelation successfully with a simple resolver. Something like this should work:

class Bookmark(models.Model):
    url = models.URLField()
    tags = GenericRelation(TaggedItem, related_query_name="bookmarks")

class BookmarkNode(graphene_django.types.DjangoObjectType):
    tags = graphene.relay.ConnectionField(TaggedItemNode)

    def resolve_tags(self, args, context, info):
        return self.tags.all()

    class Meta:
        model = Bookmark
        interfaces = (graphene.Node,)

I don’t use the reverse/parent lookup in my app so I’m not too sure how to do that. The resolver would be simple enough, but you’d need to determine the type dynamically somehow (since content_object could be any model)

It looks like graphene has support for dynamic types; there’s not much documentation but the tests might help: https://github.com/graphql-python/graphene/blob/master/graphene/types/tests/test_typemap.py https://github.com/graphql-python/graphene/blob/master/graphene/types/tests/test_union.py

The Django docs on contenttypes / generic relations are worth reading through too: https://docs.djangoproject.com/en/1.10/ref/contrib/contenttypes/

[themotu]

This ended up being simpler than expected. I feel like this could be automatic in graphene-django but haven’t dug very much.

models.py

class Bookmark(models.Model):
    url = models.URLField()
    tags = GenericRelation(TaggedItem)

schema.py

class TaggedItemType(DjangoObjectType):
    class Meta:
        model = TaggedItem

class Bookmark(DjangoObjectType):
    class Meta:
        model = Bookmark

    tags = graphene.List(TaggedItemType)

    def resolve_tags(self, args):
        return self.tags.all()

graphql query:

{
  bookmark(id:1) {
    id
    url
    tags {
      tag
    }
  }
}