I realize there are multiple topics with the same title, but the questions and answers in those threads either don’t make sense to me or are not addressing my elephant.

I have followed the instructions on Elixir School: Ecto Basics and I am stuck.

I created a new mix mix new cc. It did not generate an application.ex.

I then set up a repository by running:

$ mix ecto.gen.repo -r Cc.MySQL
* creating lib/cc
* creating lib/cc/my_sql.ex
* creating config/config.exs
Don't forget to add your new repo to your supervision tree
(typically in lib/cc/application.ex):

• I edited config.exs to add config :cc, ecto_repos: [Cc.MySQL], correct the MySQL creds and add protocol: :tcp:
  import Config

config :cc, Cc.MySQL,
  database: "ecto",
  username: "ecto",
  password: "ecto",
  hostname: "localhost",
  protocol: :tcp

config :cc, ecto_repos: [Cc.MySQL]

• I edited my_sql.ex to use MyXQL instead of the generated Postgres.

defmodule Cc.MySQL do
  use Ecto.Repo,
    otp_app: :cc,
    adapter: Ecto.Adapters.MyXQL
end

According to the Ecto documentation, I need an application.ex. So I created one in lib/cc/application.ex:

defmodule Cc.Application do
  use Application

  def start(_type, _args) do
    children = [
      Cc.MySQL,
    ]

    opts = [strategy: :one_for_one, name: Cc.Supervisor]
    Supervisor.start_link(children, opts)
  end
end

after compiling the project and running, I use an existing Schema to try insert data:

$ iex -S mix
Compiling 1 file (.ex)
Interactive Elixir (1.16.1) - press Ctrl+C to exit (type h() ENTER for help)
iex(1)> cars = %CC.Cars.Model{agent: "localhost"}
%CC.Cars.Model{
  __meta__: #Ecto.Schema.Metadata<:built, "cars">,
  id: nil,
  date: nil,
  car: nil,
  agent: "localhost",
}
iex(2)> Cc.MySQL.insert!(cars)
** (RuntimeError) could not lookup Ecto repo Cc.MySQL because it was not started or it does not exist

However if I run {:ok, pid} = Cc.MySQL.start_link() in iex directly, I will get a PID. If I then run the command Cc.MySQL.insert!(cars) I will start getting MySQL errors instead.

What am I missing that with allow my app to generate a PID for Cc.MySQL?