This is it: Smoogy's first foray into low level, macOS Software Engineering.
This app simply takes a string and uppercases it, and then saves it to a log. No, not with Swift's uppercased() function - with an Objective-C framework that interfaces with a daemon, of course.
Here's a diagram:
It starts with UpperOS, which is a SwiftUI macOS app. It passes a string to Relay - an Objective-C framework. Then, UpperXPC, a daemon that is communicated to via XPC, uppercases the string, and sends it back to Relay, which passes it onto UpperOS.
All in the name of self-improvement and education. :)