ex-mag6.ex

ex-mag6.ex

defmodule Pragmatic do
  def supervisor(worker) do
    spawn_link(fn ->
      worker_pid = spawn_link(worker)
      Process.register(worker_pid, :worker)  # <- I added this so we can find our worker
      Process.flag(:trap_exit, true)
      receive do
        {:EXIT, ^worker_pid, _} ->
          supervisor(worker)
      end
    end)
  end

  def worker(state \\ %{}) do
    receive do
      {:set, value} ->
        worker(value)

      {:get, from} ->
        send(from, state)
        worker(state)
    end
  end
end

pseudo_agent = fn -> Pragmatic.worker() end
pseudo_supervisor = Pragmatic.supervisor(pseudo_agent)
agent_pid = Process.whereis(:worker)

# Our very simple implementation does not wait until the worker process
# is actually started, so if we use this outside iex, this is a race condition!

send(worker_pid, {:set, 1})
send(worker_pid, {:get, self()})
receive do
  any -> IO.inspect any
end
#> 1

send(worker_pid, {:set, 3})
send(worker_pid, {:get, self()})
receive do
  any -> IO.inspect any
end
#> 3