Observable pattern implemented with metaprogramming

observable.ex

defmodule Observable do
  defmacro __using__(opts) do
    subscriber_modules = opts[:subscriber_modules]
    function = opts[:observable_function]
    tag = opts[:tag]

    {f, _} = Code.eval_quoted(function)

    arity = f |> :erlang.fun_info() |> Keyword.get(:arity)

    args =
      Enum.map(1..arity, fn n ->
        Macro.var(:"arg_#{n}", __MODULE__)
      end)

    quote do
      require Kernel.SpecialForms

      @doc """
      Dispatches the `function(arg)` result to the subscriber modules
      """
      def execute(unquote_splicing(args)) do
        result = unquote(function).(unquote_splicing(args))

        Enum.each(unquote(subscriber_modules), fn mod ->
          :ok = mod.receive(unquote(tag), result)
        end)

        result
      end
    end
  end
end

defmodule Subscriber1 do
  def receive(tag, result) do
    IO.puts("Sub. 1 received #{inspect(result)} from #{tag}")
  end
end

defmodule Subscriber2 do
  def receive(tag, result) do
    IO.puts("Sub. 2 received #{inspect(result)} from #{tag}")
  end
end

defmodule Executor do
  use Observable,
    subscriber_modules: [Subscriber1, Subscriber2],
    tag: :my_executor,
    observable_function: &Executor.addition/3

  @doc false
  def addition(a, b, c), do: a + b + c
end