IO

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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Setup

Ensure you type the ea keyboard shortcut to evaluate all Elixir cells before starting. Alternatively you can evaluate the Elixir cells as you read.

IO

We can use the IO module for retrieving user input and displaying output.

We can use IO.inspect/2 and IO.puts/2 print displaying information.

We can also use IO.gets/2 to retrieve input from the user.

iex> input = IO.gets("Give me some input: ")
Give me some input: sure!
"sure!\n"
iex> input
"sure!\n"

Keep in mind, this will work when running an Elixir project or in the IEx shell, but will fail with an :enotsup (error not supported) error when we run it from Livebook.

IO.gets("I will fail!")

That’s because there is no command line or other device to retrieve user input from.

Your Turn

Run IO.gets/2 in the command line from the IEx shell and bind the return value to an input variable.

iex> input = IO.gets("Give me some input: ")

Mark As Completed

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

save_name =
  case Path.basename(__DIR__) do
    "reading" -> "io_reading"
    "exercises" -> "io_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 io-reading
$ git add .
$ git commit -m "finish io reading"
$ git push origin io-reading

Create a pull request from your io-reading 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.

If you are interested in joining the next academy cohort, sign up here to receive more news when it is available.

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