Processes

import IEx.Helpers

Processes

• execute code
• hold a little state
• super lightweight
• actors

A Process

• id
• execute
• send/receive messages

client = self()

service = self()

message = "hello, world"

send(service, message)

Process.info(service)

flush()

Core

# fibonacci sequence
[1, 1, 2, 3, 5, 8, 13, 21]

defmodule Fibber.Core do
  defstruct [:a, :b]

  def new, do: %__MODULE__{a: 0, b: 1}

  def next(fib) do
    %__MODULE__{a: fib.b, b: fib.a + fib.b}
  end

  def show(%{b: b} = _fib), do: b
end

alias Fibber.Core

Core.new |> Core.next() |> Core.next() |> Core.next() |> Core.show()

Boundary

defmodule Fibber.Service do
  alias Fibber.Core
  
  def start_link() do
    spawn_link(fn -> Core.new() |> loop() end)
  end

  def loop(fib) do
    fib
    |> listen()
    |> loop()
  end

  def listen(fib) do
    receive do
      :next -> Core.next(fib)
      
      {:value, from_pid} ->
        send(from_pid, fib.b)
        fib
    end
  end

  def next(pid) do
    send(pid, :next)
  end

  def show(pid) do
    send(pid, {:value, self()})
    receive do
      value -> value 
    end
  end
end

pid = Fibber.Service.start_link()

Fibber.Service.show(pid)

Fibber.Service.next(pid)

send(pid, :next)

defmodule Fibber do
  alias Fibber.Service

  def sart_link() do
    Service.start_link()
  end

  def next(pid) do
    Service.next(pid)
  end

  def show(pid) do
    Service.show(pid)
  end
end

fibber = Fibber.sart_link()

Fibber.next(fibber)

Fibber.show(fibber)