can't create instance of a model class in models from controller class

a model is just a class , after reading namespace primer i simply created another directory within app

i'm starting with keeping things simple ( i'm only playing with CI4 at this stage) using

<?php namespace App\Andy;
use CodeIgniter\Database\ConnectionInterface;

class DoStuff

{
protected $title;
protected $article;



public function index()
{
$db = \Config\Database::connect("default");

$query = $db->query("SELECT * FROM blog");
$row = $query->getRowArray();
return $row['title'].$row['article'];


}



i can retrieve from sqlite database ; i can also insert into database