cherry1.livemd

Handling state between multiple processes with Elixir

Spawning a process

Code from the Handling state between multiple processes with elixir, a blog post by Cherry Ramatis.

pid = spawn(fn -> IO.puts("teste") end)

pid

Process.alive?(pid)

Spawning another process

pid =
  spawn(fn ->
    :timer.sleep(10000)
    IO.puts("teste")
  end)

Process.alive?(pid)

Wait a few seconds, until "test" appears above.

Process.alive?(pid)

Listener module

defmodule Listener do
  def call do
    receive do
      {:hello, msg} -> IO.puts("Received: #{msg}")
    end
  end
end

pid = spawn(&Listener.call/0)

send(pid, {:hello, "Hello World"})

Tasks

task =
  Task.async(fn ->
    IO.puts("Task is running")
    42
  end)

IO.puts("a code")

answer_to_everything = Task.await(task)

answer_to_everything

Listener2

defmodule Listener2 do
  def call do
    receive do
      {:print, msg} -> IO.puts("Received message: #{msg}")
    end
  end
end

{:ok, pid} = Task.start(&Listener2.call/0)

send(pid, {:print, "Eat more fruits"})

Designing state with the Agent wrapper

{:ok, agent} = Agent.start_link(fn -> [] end)

agent

Agent.update(agent, fn list -> ["elixir" | list] end)

Agent.get(agent, fn list -> list end)