When developing the ACES app, I found some Youtubers to be pretty useful.
This video tutorial (a bit outdated) helped me learn the basics of Swift/iOS development: https://www.youtube.com/watch?v=5b91dFhZz0g
I also watched some videos from the "Let's Build That App" Youtube channel. He has many videos on how to do more specific things in Swift/iOS:
Both of these Youtubers have some pretty good videos on how Swift/iOS ties into various services from Google's Firebase.