How To Set Up Default Values For Embeded Resources in forms?

Hello, I set up an ash resource that has some embedded resources.

(As a side note, I’d love some array helpers for the ash_forms, as I didn’t really want to create embedded resources in the first place, it could have just been an {:array, :string} but I didn’t see a clean way to map that to the helpers that exist currently! If you agree I’d love to help out with a PR on that)

But I’m trying to render some default values in the forms, and I don’t quite understand how to do that. My form looks like this currently.

      AshPhoenix.Form.for_create(RunConfigData, :create,
        api: Smol.Pipelines,
        actor: socket.assigns.current_user,
        forms: [
          models: [
            type: :list,
            resource: Model,
            data: [
              %{
                "model" => "gpt-4o"
              },
              %{
                "model" => "claude-3-opus-20240229"
              }
            ],
            create_action: :create,
            update_action: :update
          ],
          messages: [
            type: :list,
            resource: Message,
            data: [
              %{
                "message" => "msg1"
              },
              %{
                "message" => "msg2"
              }
            ],
            create_action: :create,
            update_action: :update
          ]
        ]
      )
      |> to_form()

And when I render the forms with the inputs_for:

            <.inputs_for :let={model_form} field={@run_config_form[:models]}>
              <div class="flex space-x-2 mt-1">
                <.input
                  type="text"
                  field={model_form[:model]}
                  phx-debounce="blur"
                  class="block w-full shadow-sm sm:text-sm border-gray-300 rounded-md"
                />
              </div>
            </.inputs_for>

It works in the sense that it will render two inputs, so it’s being picked up and that’s great, but I’d like those default value I set in the liveview to populate the value of the input when the page is first loaded.

So the question is, in this situation how do I access the value of the object in the inputs_for loop?

I do it with the other values in my form that aren’t embedded resources in the actual action of the resource like this:

defmodule Smol.Pipelines.RunConfigData do
  alias Smol.Pipelines.{Model, Message}

  use Ash.Resource,
    # Use in-memory storage since it doesn't need to persist
    data_layer: Ash.DataLayer.Ets

  attributes do
    uuid_primary_key :id
    attribute :repository_location_name, :string, allow_nil?: false
    attribute :job_name, :string, allow_nil?: false

    attribute :data_fetch_end_time, :utc_datetime, allow_nil?: false
    attribute :data_fetch_duration_hours, :integer, allow_nil?: false
    attribute :list_id, :integer, allow_nil?: false

    attribute :models, {:array, Model}, allow_nil?: false
    attribute :messages, {:array, Message}, allow_nil?: false
    attribute :system_prompt, :string, allow_nil?: false
    attribute :overrides, :map, allow_nil?: true
  end

  actions do
    defaults [:update]

    create :create do
      change fn changeset, _ ->
        changeset
        |> maybe_set_default(:repository_location_name, "data_ingestion")
        |> maybe_set_default(:job_name, "data_summary_job")
        |> maybe_set_default(:list_id, 1_585_430_245_762_441_216)
        |> maybe_set_default(:system_prompt, "Put your system prompt here")
        |> maybe_set_default(:data_fetch_duration_hours, 24)
        |> maybe_set_default(:overrides, nil)
      end
    end
  end

  defp maybe_set_default(changeset, field, default_value) do
    if Ash.Changeset.get_attribute(changeset, field) == nil do
      Ash.Changeset.change_attribute(changeset, field, default_value)
    else
      changeset
    end
  end
end

But I don’t quite understand how I would do that in the embedded resources.

Sorry if all of this isn’t quite clean, I’m quite new to Ash and am still getting my footing on how to do things, so please let me know if I’m doing something weird!