Billzabob
Using Absinthe Dataloader for top level queries
I’m trying to figure out how to use Dataloader with absinthe for a top level query. I have it working just fine for a field on an object, like so:
defmodule UserSchema do
use Absinthe.Schema.Notation
import Absinthe.Resolution.Helpers, only: [dataloader: 1]
alias Core.Loaders.CardLoader
object :user do
field(:cards, list_of(:card), resolve: dataloader(CardLoader))
end
end
However, I’d like to also be able to use Dataloader for top level queries like so:
query do
field(:cards, list_of(:card), resolve: dataloader(CardLoader))
end
But this fails with this error:
** (Dataloader.GetError) The given atom - :cards - is not a module.
This can happen if you intend to pass an Ecto struct in your call to
`dataloader/4` but pass something other than a struct.
How can I achieve this? I could obviously do it another way, by having the resolver function call Repo.all(Card) but I’d love to be able to do it all with Dataloader. Is that possible?
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Billzabob
I ended up getting this working with the following:
import Absinthe.Resolution.Helpers, only: [on_load: 2]
query do
field :users, list_of(:user) do
arg(:ids, non_null(list_of(:id)))
resolve(fn %{ids: ids}, %{context: %{loader: loader}} ->
loader
|> Dataloader.load_many(UserLoader, User, ids)
|> on_load(fn loader ->
users = Dataloader.get_many(loader, UserLoader, User, ids)
{:ok, users}
end)
end)
end
end
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