So, the secret's out — because I'm scheduled to do a talk at Ann Arbor CocoaHeads on Thursday — that the new book I've been working on is all about Xcode. Rather than being a API guide to an SDK, this book is all about the Xcode app itself, and all the things it can do for you that you might not have realized. To that end, the book happily intermingles examples from iOS, macOS, and even tvOS and watchOS, using Swift, Objective-C and even procedural C.
To kick off a series of videos with demos from the book, here's an introduction to debugging with breakpoints. You'll see how to use breakpoints to step through your code and analyze the program's state, to help figure out what your code is doing and why. This episode also looks at some of the additional features of Xcode breakpoints, like stopping only if a certain condition is true, logging messages when the breakpoint is hit, and even playing short sounds to debug high-speed conditions like gesture tracking.
Xcode on the Mac App Store: geo.itunes.apple.com/us/app/xcode/id497799835?mt=12&at=10l4Gc
Xcode Treasures eBook: pragprog.com/book/caxcode/xcode-treasures