lecture 04

lectures/04/counter2/lib/counter/application.ex

@@ -0,0 +1,21 @@
+defmodule Counter.Application do
+  # See https://hexdocs.pm/elixir/Application.html
+  # for more information on OTP Applications
+  @moduledoc false
+
+  use Application
+
+  @impl true
+  def start(_type, _args) do
+    children = [
+      # Starts a worker by calling: Counter.Worker.start_link(arg)
+      Supervisor.child_spec({Counter.Worker, :c1}, id: :counter1),
+      Supervisor.child_spec({Counter.Worker, :c2}, id: :counter2)
+    ]
+
+    # See https://hexdocs.pm/elixir/Supervisor.html
+    # for other strategies and supported options
+    opts = [strategy: :one_for_one, name: Counter.Supervisor]
+    Supervisor.start_link(children, opts)
+  end
+end

lectures/04/counter2/lib/counter/worker.ex

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+defmodule Counter.Worker do
+  use GenServer
+
+  # client
+  def start_link(name) do
+      GenServer.start_link(__MODULE__, nil, name: name)
+  end
+
+  def inc(name, amt \\ 1) do
+      GenServer.cast(name, {:inc, amt})
+  end
+
+  def value(name) do
+    GenServer.call(name, :value)
+  end
+
+  # server impl
+  @impl true
+  def init(_arg) do
+    {:ok, 0}
+  end
+
+  @impl true
+  def handle_call(:value, _from, state) do
+      {:reply, state, state}
+  end
+
+  @impl true
+  def handle_cast({:inc, amt}, state) do
+      {:noreply, state + amt}
+  end
+
+  # for demonstration only
+  @impl true
+  def handle_info(:reset, _state) do
+    {:noreply, 0}
+  end
+end