elixir recursion example

recursion.ex

defmodule BackOfficeApp.Customer do
  use BackOfficeApp.Web, :model

  @primary_key {:id, :binary_id, autogenerate: true}

  schema "customers" do
    field :title, :string
    field :first_name, :string
    field :middle_name, :string
    field :last_name, :string
    field :company_name, :string
    field :is_active, :boolean, default: false
    field :email, :string
    field :phone, :string
    field :mobile, :string
    field :fax, :string
    field :website, :string
    field :notes, :string

    timestamps()
  end

  @doc """
  Builds a changeset based on the `struct` and `params`.
  """
  def changeset(struct, params \\ %{}) do
    struct
    |> cast(params, [:title, :first_name, :middle_name, :last_name, :company_name,
                     :is_active, :email, :phone, :mobile, :fax, :website, :notes])
    |> validate_required([:first_name, :email])
    |> capitalize([:title, :first_name, :middle_name, :last_name])
  end

  defp capitalize(changeset, fields) do
    changeset
    |> update_many_changes(fields, &(String.capitalize(&1)))
  end

  defp update_many_changes(changeset, [h| t], f) do
    changeset |> update_change(h, f) |> update_many_changes(t, f)
  end

  defp update_many_changes(changeset, [], _), do: changeset
end