Autoload classes via Composer on hosting?

Question

PHP

Good afternoon, I recently started studying composer, after googling a little I implemented class autoloading for my project, it works locally, but Fatal error: Class not found
falls out on the hosting I don’t quite understand how it works at all, and whether it should work, whether something change or some other reason?

.json

{
  "name": "artberg",
  "require": {},

  "autoload": {
    "psr-4": {
      "App\\": "app/"
    }
  }
}

index.php
require(__DIR__ . '/vendor/autoload.php');

Answer 1

Composer's instructions say this:

After adding the autoload field, you have to re-run dump-autoloadto re-generate the vendor/autoload.php file.
https://getcomposer.org/doc/01-basic-usage.md#auto...
Bottom line:
That is, you need to run the commandcomposer dump-autoload