Just a PSA sending messages to processes in Elixir has changed in the latest versions. In Elixir 0.12.1 sending messages used <-

defmodule CustomModule do
  def spawn_process() do
    spawn(fn() -> display_message() end)
  end

  defp display_message() do
    receive do
      {:ok, message} ->
        IO.puts message
    end
  end
end

Processing.spawn_process() <- {:ok, "testing"}

In 0.12.2 <- is deprecated, and removed in 0.12.3. You have to use send/2.

send(pid, message) like so:

defmodule CustomModule do
  def spawn_process() do
    spawn(fn() -> display_message() end)
  end

  defp display_message() do
    receive do
      {:ok, message} ->
        IO.puts message
    end
  end
end

send(Processing.spawn_process(), {:ok, "testing"})

This caused me a little grief because I wasn't aware so I figured it might help some people save some time.

Adam has worked with Isotope 11 for 4 years and has been a professional software developer for over 12 years. He has been lead developer on multiple Fortune 500 projects. He is the author of "Beginning Rails 4" which was published by Apress in September 2013.