batching.ex

# User has many storages.
#
# Give me a user, along with the storages it owns.
# q={user(id: 131) {name, storages{title} }}

defmodule Users.Types do
  use Absinthe.Schema.Notation

  object :user do
    field :id, :id
    field :first_name, :string
    field :last_name, :string
    field :email, :string
    field :phone, :string
    field :storages, :storage do
      resolve fn user, _, _ ->
        batch({ApiEndpoint.Schema.Helpers, :by_id, Storages.Storage}, {:user_id, user.id}, fn batch_result ->
          # Find the storages for the user, in the batch.
          storages = Enum.filter(batch_result, fn storage -> storage.user_id == user.id end)
          
          # It seems i may not return a list of storages here? 
          {:ok, batch_result}
        end)
      end
    end
  end
end

defmodule ApiEndpoint.Schema.Helpers do
  def by_id(model, acc) do
    Enum.reduce(acc, model, fn {foreign_key, id}, query ->
      query
      |> where([m], field(m, ^foreign_key) == ^id)
    end)
    |> Storages.Repo.all # But there are no database in the Endpoint! Solve plox?
  end
end

# > expected a map, got: [%Storages.Storage{price_annually..........