Example serializing an arbitrary elixir structure as xml and returning it from a phoenix endpoint

a_controller.ex

defmodule WhateverWeb.AController do
  use WhateverWeb, :controller
  
  # get  "/whatever/:format", WhateverWeb.AController, :some_action
  def some_action(conn, %{"format" => "xml"} = _params) do
    example_data = %{
      name: "Buy Guy",
      title: "buyer",
      items: [
        %{name: "A", cost: 10, qty: 1},
        %{name: "B", cost: 10, qty: 2}
      ]
    }
    
    xml =
      %{root_container: example_data}
      |> to_xml
      |> XmlBuilder.generate

    conn
    |> put_resp_content_type("text/xml")
    |> send_resp(200, xml)
  end
  def some_action(conn, _params) do
    conn
    |> send_resp(404, "Not found")
  end

  defp to_xml(data) when is_list(data) or is_map(data) do
    data
    |> Enum.map(&to_xml/1)
  end
  defp to_xml({k, v}) do
    {k, %{}, to_xml(v)}
  end
  defp to_xml(v), do: v

end