Elixir: Notes on Supervisor and Application

The repo backing this code is here.

It is literally a result of me working through the docs, nothing original.

Supervisor and Application

Supervisor code

defmodule KV.Supervisor do
  use Supervisor

  def start_link do
    Supervisor.start_link(__MODULE__, :ok)
  end

  def init(:ok) do
    children = [
      worker(KV.Registry, [KV.Registry])
    ]

    supervise(children, strategy: :one_for_one)
  end
end

Key points:

1. ` worker(KV.Registry, [KV.Registry]) this calls KV.Registry.start_link(KV.Registry)`
2. This means that the KV.Registry needs to take a name as an argument

We could now do this:

iex> KV.Supervisor.start_link
{:ok, #PID<0.66.0>}
iex> KV.Registry.create(KV.Registry, "shopping")
:ok
iex> KV.Registry.lookup(KV.Registry, "shopping")
{:ok, #PID<0.70.0>}

But we don’t, we use an application

Application

To start iex and be able to use the observer gui you need this command line iex --erl "-smp" -S mix