My first experience with Swift ended in me infecting myself with a virus (kinda). I wanted to create a macOS app that would listen for a global key event, catch it and then type a word.

During development I set it up to listen for ANY key event and to type "BALLS". So what happened? I compiled the code, everything looked good, I started the app and pressed a key which emitted a key event. The event was caught by my app and it typed "BALLS", just as expected. However, the typing of the word caused a NEW key event to be emitted, which the app also caught. The infinite loop was a fact. FUCK!

I tried closing down XCode but all I could see was "BALLS BALLS BALLS" everywhere. I tried everything I knew but it just kept typing "BALLS". I had to hold down my power button to make it stop.

I finally finished the app (which I named "The Balls App", I kept the word "BALLS"). I solved this issue by only listening for KeyUp and when emitting the "BALLS" word I just used KeyDown.