I tried to learn Elixir a few years ago and stopped. I am trying again.
In the code below I have a GenServer that is started by a Supervisor. When I compile the code it works as expected - if the GenServer is manually killed the Supervisor restarts it.
This is good and does what I expect.
I now want to wrap my code as an “Application”.
Thus I go to mix.exs and in the application method I update the code to reference my Module
def application do
[
extra_applications: [:logger],
mod: {App, []}
]
end
When I compile my code I get the following error:
18:49:32.437 [notice] Application todos exited: exited in: App.start(:normal, [])
** (EXIT) an exception was raised:
** (UndefinedFunctionError) function App.start/2 is undefined (module App is not available)
App.start(:normal, [])
(kernel 8.5) application_master.erl:293: :application_master.start_it_old/4
** (Mix) Could not start application todos: exited in: App.start(:normal, [])
** (EXIT) an exception was raised:
** (UndefinedFunctionError) function App.start/2 is undefined (module App is not available)
App.start(:normal, [])
(kernel 8.5) application_master.erl:293: :application_master.start_it_old/4
I am not sure what the error is inferring is wrong nor do I know how to fix it. I would like to know how to fix it and why the error occurs.
My full code is below
todos/lib/todos.ex
defmodule App.Service do
use GenServer
def start_link(state) do
GenServer.start_link(__MODULE__, state, name: __MODULE__)
end
def init(state) do
{:ok, state}
end
def get_state(pid) do
GenServer.call(pid, :get_state)
end
def set_state(pid,state) do
GenServer.call(pid, {:set_state, state})
end
def handle_call(:get_state, _from, state) do
{:reply, state, state}
end
def handle_call({:set_state, new_state}, _from, state)do
{:reply,state,[new_state | state]}
end
end
defmodule App.Supervisor do
use Supervisor
def start do
Supervisor.start_link(__MODULE__, [])
end
def init(_) do
children = [
{App.Service,[]}
]
Supervisor.init(children, strategy: :one_for_one)
end
end
todos/lib/mix.exs
defmodule Todos.MixProject do
use Mix.Project
def project do
[
app: :todos,
version: "0.1.0",
elixir: "~> 1.14",
start_permanent: Mix.env() == :prod,
deps: deps()
]
end
def application do
[
extra_applications: [:logger],
mod: {App, []}
]
end
defp deps do
[
]
end
end
