Hey Felix, Chapter 4 only has you exploring iOS applications, not macOS applications. There’s no need to open up Terminal to attach to Xcode.
Xcode will link to AppKit so there won’t be any UIViewControllers but there will be NSViewControllers (i.e. if you were exploring Xcode, you could query via (lldb) image loo -n "-[NSViewController viewDidLoad]", but that’s not what Chapter 4 wants you to do)
Explore the Signals iOS application via Xcode’s console. Through here, you’ll find the UIKit method -[UIViewController viewDidLoad]
Yeah, I was also confused here also, I was trying to follow along in the Terminla’s LLDB. You should better the book by adding “in Xcode’s console” where appropriate. I just spent an hour or two debugging!