I want to integrate my web app with Shopify which means I have to create my own Shopify app. I noticed that Shopify requires self hosting so it would benefit me to add the Shopify app as part of my already existing web app because I can host it together.
Does this seem possible or do I have to make a desperate application?
It should totally be possible to add a shopify app to your existing ruby on rails project.
If you look at https://github.com/Shopify/shopify_app all you have to do is add in shopify_app to your gem file and then generate the proper routes. You can use their built-in generators or manually make the routes yourself.
Basically you would just need to make additional routes for your existing application to handle the requests to and from Shopify.