ecto_mapping.ex

defmodule ExternalUser do
  use Ecto.Schema

  import Ecto.Changeset

  @primary_key false
  embedded_schema do
    field(:first_name, :string)
    field(:last_name, :string)
  end

  @fields ~w(first_name last_name)a

  def changeset(params) do
    %__MODULE__{}
    |> cast(params, @fields)
  end

  def create(params) do
    ch = changeset(params)

    if ch.valid? do
      {:ok, apply_changes(ch)}
    else
      {:error, ch}
    end
  end

  def to_profile(%{first_name: first, last_name: last}) do
    %{name: "#{first} #{last}"}
  end
end

data = %{"first_name" => "Jorge", "last_name" => "Vilaça"}
{:ok, user} = ExternalUser.create(data)
ExternalUser.to_profile(user)