Xcode 10.1
If you have Bundler run:
$ sh setup.sh
As a rule I don't use comments. I think comments usually are a code smell and can be easily fixed with a function extraction.
However, in this POC I've placed few comments. The reason behind this is to give you (the reviewer) hints why I've decided to implement a particular thing in that way.
Those comments are what I would answer if someone asks me "why this way?" during the code review. Such comments are marked with // mark.
I've focused on architecting the app, not on how it looks. I'm sorry for that ;).