Games: Supervisor Setup

Mix.install([
  {:jason, "~> 1.4"},
  {:kino, "~> 0.8.0", override: true},
  {:youtube, github: "brooklinjazz/youtube"},
  {:hidden_cell, github: "brooklinjazz/hidden_cell"}
])

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Games: Supervisor Setup

We’ve seen we can initialize a new mix project with a supervisor using the --sup flag when we create a mix project. Now, you’re going to add a supervisor to your existing Games project.

Configure Games.Application

Supervised Mix projects include an Application module.

> ### Application > > A module for working with applications and defining application callbacks. > Applications are the idiomatic way to package software in Erlang/OTP. To get the idea, they are similar to the “library” concept common in other programming languages, but with some additional characteristics. > An application is a component implementing some specific functionality, with a standardized directory structure, configuration, and life cycle. Applications are loaded, started, and stopped. Each application also has its own environment, which provides a unified API for configuring each application. > > HexDocs: Application

Create a lib/games/application.ex file with the following content. This will be the callback function that starts your application supervisor.

We’ve included an IO.puts/2 statement to demonstrate that the supervisor does start. This is not strictly necessary but will allow you to test that you have configured this correctly later.

defmodule Games.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
    IO.puts("Starting Games.Application")
    children = []

    # See https://hexdocs.pm/elixir/Supervisor.html
    # for other strategies and supported options
    opts = [strategy: :one_for_one, name: Games.Supervisor]
    Supervisor.start_link(children, opts)
  end
end

Configure Games.MixProject

In lib/mix.exs configure the application callback module using the :mod option in the Games.MixProject.application/1 function. This tells your mix project to run the Games.Application.start/2 function you just defined.

def application do
  [
    extra_applications: [:logger],
    mod: {Games.Application, []}
  ]
end

Test your application from the command line by running mix run. You should see your IO.puts/2 message confirming the application does start the supervisor.

$ mix run
Compiling 1 file (.ex)
Starting Games.Application

The same will print if you start the application in the IEx shell.

$ iex -S mix
...
Starting Games.Application
...

Mark As Completed

file_name = Path.basename(Regex.replace(~r/#.+/, __ENV__.file, ""), ".livemd")

save_name =
  case Path.basename(__DIR__) do
    "reading" -> "games_supervisor_setup_reading"
    "exercises" -> "games_supervisor_setup_exercise"
  end

progress_path = __DIR__ <> "/../progress.json"
existing_progress = File.read!(progress_path) |> Jason.decode!()

default = Map.get(existing_progress, save_name, false)

form =
  Kino.Control.form(
    [
      completed: input = Kino.Input.checkbox("Mark As Completed", default: default)
    ],
    report_changes: true
  )

Task.async(fn ->
  for %{data: %{completed: completed}} <- Kino.Control.stream(form) do
    File.write!(
      progress_path,
      Jason.encode!(Map.put(existing_progress, save_name, completed), pretty: true)
    )
  end
end)

form

Commit Your Progress

Run the following in your command line from the curriculum folder to track and save your progress in a Git commit. Ensure that you do not already have undesired or unrelated changes by running git status or by checking the source control tab in Visual Studio Code.

$ git checkout -b games-supervisor-setup-exercise
$ git add .
$ git commit -m "finish games supervisor setup exercise"
$ git push origin games-supervisor-setup-exercise

Create a pull request from your games-supervisor-setup-exercise branch to your solutions branch. Please do not create a pull request to the DockYard Academy repository as this will spam our PR tracker.

DockYard Academy Students Only:

Notify your teacher by including @BrooklinJazz in your PR description to get feedback. You (or your teacher) may merge your PR into your solutions branch after review.

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