Hi

I had this piece of (working) code:

    items =
      products
      |> Enum.map(fn product ->
        params = %{product_id: product.id}

        Snapshot.new_item_changeset(
          %Snapshot.Item{
            product: product
          },
          params
        )
      end)

That later created a form with:

    form =
      Ecto.Changeset.put_embed(
        Ecto.Changeset.change(%Snapshot{}),
        :items,
        items
      )
      |> to_form

That I was rendering as:

    <.form for={@form} phx-change="validate" phx-submit="save">
      <.inputs_for :let={snapshot} field={@form[:items]}>
        <div><%= snapshot.data.product.description %></div>

However, since I didn’t want to repeat that Ecto.Changeset.put_embed( I wanted to move that logic to the schema as:

  def changeset(snapshot, params \\ %{}) do
    snapshot
    |> cast(params, [])
    |> cast_embed(:items, with: &new_item_changeset/2)
  end

  def new_item_changeset(item, params \\ %{}) do
    item
    |> cast(params, [:quantity, :product_id, :rate_id])
    |> validate_number(:quantity, greater_than_or_equal_to: 0)
  end

But if I move the original code to:

    items =
      products
      |> Enum.map(fn product ->
        %{product_id: product.id}
      end)

And then just:

    form =
      Snapshot.changeset(%Snapshot{}, %{items: items})
      |> to_form

That works, however the template doesn’t have a product loaded ending up in the following error:

key :description not found in: #Ecto.Association.NotLoaded<association :product is not loaded>

It would be easy to fix this with a Repo.preload but since it’s an embedded schema I am not sure where to do that.