Hey @ngscheurich!

The GraphQL type system only permits unions between objects. This leads to the following slightly cumbersome solution:

object :boolean_value do
  field :value, non_null(:boolean)
end

object :string_value do
  field :value, non_null(:string)
end

object :string_list do
  field :value, list_of(:string)
end

union :payload do
  types [:string_value, :string_list, :boolean_value]

  resolve_type fn payload ->
    #exercise for the reader
  end
end

Thanks for the quick response, @benwilson512!

So, it seems like I was sort of on the right path, which is a nice sanity check. Here’s the code I was working on:

 object :boolean_payload do
    field(:value, :boolean)
  end

  object :string_payload do
    field(:value, :string)
  end

  object :list_payload do
    field(:value, list_of(:string))
  end

  union :payload do
    types([:boolean_payload, :string_payload, :list_payload])
    resolve_type(&resolve_payload_value/2)
  end

  defp resolve_payload_value(value, _) when is_boolean(value),
    do: :boolean_payload

  defp resolve_payload_value(value, _) when is_binary(value),
    do: :string_payload

  defp resolve_payload_value(value, _) when is_list(value),
    do: :list_payload

My confusion is around how to write the query, e.g., what I should sub-select on payload here:

query ($elderId: String!, $datapointName: String!, $count: Int) {
  datapointsForElder(elderId: $elderId, datapointName: $datapointName, count: $count) {
    name,
  	type,
    payload {
      ???
    }
  }
}

I’m looking at inline fragments at the moment, like ... on BooleanPayload { value } but something about that doesn’t seem quite right…

It seems like I have more of GraphQL problem, so I’ll study up on that part of the equation—any advice is, of course, appreciated though.

P. S. Looking forward to seeing you at The Big Elixir this week!

This is really more of an ecto qustion than an Absinthe question. I’d use a custom ecto type that always returned dates instead of sometimes an atom. Your GraphQL clients shouldn’t know or care that you’re using mysql.