metaprogramming in elixir

source.ex

defmodule BaseApp do
  def new_conn do
    %{}
    |> put_status(:ok)
  end

  def render(%{status: status} = conn) do
    IO.puts "Status: #{status}"
    conn
  end

  def put_status(conn, status) when is_atom(status) do
    status_code = case status do
      :ok ->
        200
      :bad_request ->
        400
      :not_found ->
        404
      _ ->
        exit("Invalid status atom")
    end

    put_status(conn, status_code)
  end

  def put_status(conn, status) when is_number(status) do
    put_in(conn[:status], status)
  end
end

defmodule MyApp do
  import BaseApp

  def index(conn) do
    conn
    |> put_status(:not_found)
  end

  def run do
    new_conn
    |> index
    |> render
  end
end

MyApp.run