amokan · July 21, 2022 11:12 · Jan 28, 2019 · Jan 28, 2019 · Jan 28, 2019
diff --git a/grocery_cart_old.ex b/grocery_cart_old.ex
@@ -25,14 +25,14 @@ defmodule GroceryCartOld do
   def handle_info(:add_cheese, %__MODULE__{items: items} = state) do
     updated_state = %__MODULE__{state | items: ["cheese" | items]}
 
-    # queues up a msg to itself using `send()` with a message format that will be picked up by a `handle_cast/2` callback
-    send(self(), {:"$gen_cast", :add_milk})
+    # queues up a msg to itself using `send()` which will be picked up by a `handle_info/2` callback
+    send(self(), :add_milk)
 
     {:noreply, updated_state}
   end
 
   @doc false
-  def handle_cast(:add_milk, %__MODULE__{items: items} = state) do
+  def handle_info(:add_milk, %__MODULE__{items: items} = state) do
     updated_state = %__MODULE__{state | items: ["milk" | items]}
 
     # queues up a msg to itself using `Process.send_after()` with a delay of 1 second - this will be picked up by a `handle_info/2` callback

diff --git a/grocery_cart_new.ex b/grocery_cart_new.ex
@@ -0,0 +1,42 @@
+defmodule GroceryCart do
+  @moduledoc """
+  Simple example showing the `handle_continue` callback in Erlang/OTP 21+
+  """
+
+  use GenServer
+
+  # simple contrived struct for state - didn't need to be a struct at all
+  defstruct items: []
+
+  @doc """
+  Start a new instance of the Grocery Cart server
+  """
+  def start_link, do: GenServer.start_link(__MODULE__, :ok, name: __MODULE__)
+
+  @doc false
+  def init(_) do
+    {:ok, %__MODULE__{}, {:continue, :add_cheese}}
+  end
+
+  @doc false
+  def handle_continue(:add_cheese, %__MODULE__{items: items} = state) do
+    updated_state = %__MODULE__{state | items: ["cheese" | items]}
+
+    {:noreply, updated_state, {:continue, :add_milk}}
+  end
+
+  @doc false
+  def handle_continue(:add_milk, %__MODULE__{items: items} = state) do
+    updated_state = %__MODULE__{state | items: ["milk" | items]}
+
+    {:noreply, updated_state, {:continue, :print_and_exit}}
+  end
+
+  @doc false
+  def handle_continue(:print_and_exit, %__MODULE__{items: items} = state) do
+    IO.inspect(items, label: "Items")
+    IO.puts("Will Exit Now")
+
+    {:stop, :normal, state}
+  end
+end
diff --git a/grocery_cart_old.ex b/grocery_cart_old.ex
@@ -5,7 +5,7 @@ defmodule GroceryCartOld do
 
   use GenServer
 
-
+  # simple contrived struct for state - didn't need to be a struct at all
   defstruct items: []
 
   @doc """
@@ -44,7 +44,6 @@ defmodule GroceryCartOld do
   @doc false
   def handle_info(:print_and_exit, %__MODULE__{items: items} = state) do
     IO.inspect(items, label: "Items")
-
     IO.puts("Will Exit Now")
 
     {:stop, :normal, state}

diff --git a/grocery_cart_old.ex b/grocery_cart_old.ex
@@ -0,0 +1,52 @@
+defmodule GroceryCartOld do
+  @moduledoc """
+  Simple example showing how to orchestrate a GenServer progressing it's own state
+  """
+
+  use GenServer
+
+
+  defstruct items: []
+
+  @doc """
+  Start a new instance of the Grocery Cart server
+  """
+  def start_link, do: GenServer.start_link(__MODULE__, :ok, name: __MODULE__)
+
+  @doc false
+  def init(_) do
+    # queues up a msg to itself using `send()` which will be picked up by a `handle_info/2` callback
+    send(self(), :add_cheese)
+
+    {:ok, %__MODULE__{}}
+  end
+
+  @doc false
+  def handle_info(:add_cheese, %__MODULE__{items: items} = state) do
+    updated_state = %__MODULE__{state | items: ["cheese" | items]}
+
+    # queues up a msg to itself using `send()` with a message format that will be picked up by a `handle_cast/2` callback
+    send(self(), {:"$gen_cast", :add_milk})
+
+    {:noreply, updated_state}
+  end
+
+  @doc false
+  def handle_cast(:add_milk, %__MODULE__{items: items} = state) do
+    updated_state = %__MODULE__{state | items: ["milk" | items]}
+
+    # queues up a msg to itself using `Process.send_after()` with a delay of 1 second - this will be picked up by a `handle_info/2` callback
+    Process.send_after(self(), :print_and_exit, 1_000)
+
+    {:noreply, updated_state}
+  end
+
+  @doc false
+  def handle_info(:print_and_exit, %__MODULE__{items: items} = state) do
+    IO.inspect(items, label: "Items")
+
+    IO.puts("Will Exit Now")
+
+    {:stop, :normal, state}
+  end
+end