Warning: require(/var/www/vendor/autoload.php): - laravel

Question

I am good with API creation but not so good when it comes to set up the system, I was trying to learn setting laravel with docker and was referring:
https://medium.com/#shakyShane/laravel-docker-part-1-setup-for-development-e3daaefaf3c
I followed all the steps correctly but on running:
docker-compose exec app php artisan key:generate
I am getting error:
Warning: require(/var/www/vendor/autoload.php): failed to open stream: No such file or directory in /var/www/artisan on line 18
Fatal error: require(): Failed opening required '/var/www/vendor/autoload.php' (include_path='.:/usr/local/lib/php') in /var/www/artisan on line 18
Am I wrong to assume that this problem is because the composer hasn't run!!
My Project folder is in Desktop
my docker-compose.yml is written like:
# The Application
`app:`
`build:`
`context: ./`
`dockerfile: app.dockerfile`
`working_dir: /var/www`
`volumes:`
`- ./:/var/www``
` environment:`
`- "DB_PORT=3306"`
`- "DB_HOST=database"`
# The Web Server
`web:`
`build:`
`context: ./`
`dockerfile: web.dockerfile`
`working_dir: /var/www`
`volumes_from:`
`- app`
`ports:`
`- 8080:80`
I checked other solutions on the web but I couldn't quite understand how I need to do.

Answer 1

I think it is not a good idea to follow the steps provided in the website since the
composer image is DEPRECATED
you must use the newest one from here