Timer

Mix.install([
  {:jason, "~> 1.4"},
  {:kino, "~> 0.9", override: true},
  {:youtube, github: "brooklinjazz/youtube"},
  {:hidden_cell, github: "brooklinjazz/hidden_cell"}
])

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Timer

You’re going to create a Timer GenServer.

Requirements

• The initial timer state starts as an integer 0 number of seconds.
• After spawning, the Timer should send itself a message every second to increment the timer.
• Create the start_link/1 and get_time/1 client API functions to start the timer and retrieve the current time.
• Define any necessary server callbacks.

{:ok, pid} = Timer.start_link([])
Timer.get_time(pid)
0
Process.sleep(1500)
Timer.seconds(pid)
1

Keep in mind, we cannot guarantee perfect timing when sending messages on an interval, and that is not the purpose of this exercise.

Example Solution

defmodule Timer do
  use GenServer

  def start_link(_opts) do
    GenServer.start_link(__MODULE__, [])
  end

  def get_time(timer_pid) do
    GenServer.call(timer_pid, :get_time)
  end

  @impl true
  def init(_opts) do
    schedule_timer()
    {:ok, 0}
  end

  @impl true
  def handle_info(:increment, state) do
    schedule_timer()
    {:noreply, state + 1}
  end

  @impl true
  def handle_call(:get_time, _from, state) do
    {:reply, state, state}
  end

  defp schedule_timer do
    Process.send_after(self(), :increment, 1000)
  end
end

Implement the Timer module as documented below.

defmodule Timer do
  @moduledoc """
  iex> {:ok, pid} = Timer.start_link([])
  iex> Timer.seconds(pid)
  0
  iex> Process.sleep(1200)
  iex> Timer.seconds(pid)
  1
  """
  use GenServer

  def start_link(_opts) do
  end

  def get_time(timer_pid) do
  end
end

Commit Your Progress

DockYard Academy now recommends you use the latest Release rather than forking or cloning our repository.

Run git status to ensure there are no undesirable changes. Then run the following in your command line from the curriculum folder to commit your progress.

$ git add .
$ git commit -m "finish Timer exercise"
$ git push

We’re proud to offer our open-source curriculum free of charge for anyone to learn from at their own pace.

We also offer a paid course where you can learn from an instructor alongside a cohort of your peers. We will accept applications for the June-August 2023 cohort soon.

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