struct2.exs

defmodule Attendee do
  defstruct name: "", paid: false, over_18: true

  def may_attend_after_party(%Attendee{} = attendee) do
     attendee.paid && attendee.over_18
  end

  def print_vip_badge(%Attendee{name: name }) when name != "" do
    IO.puts "Very cheap badge for #{name}"
  end

  def print_vip_badge(%Attendee{}) do
    raise "missing name for badge"
  end
end