We’ve gone through most of the features of the Swift language. From this point the bottleneck becomes learning the various Cocoa frameworks, which is out of the scope of this book.
Here are some resources for moving on to building iOS or OS X apps in Swift.
Building apps in Xcode for iOS or OS X is quite visual. You spend a lot of time building your UI in Xcode, dragging components around, setting constraints and heavily using the visual development features of Xcode. Because of this, I think that video is a much better medium for teaching and learning how to develop for iOS than text – at least until you are comfortable with using Xcode and Interface Builder to build your UI and connect it to your controllers.
Developing iOS 8 Apps with Swift is an excellent course from Stanford is available for free on iTunes University. It should be your first stop if you’re interested in building iOS apps. For more (paid) video courses check out Bitfountain and Udemy, both of which have good introductory courses in iOS development – at least until you are familiar with how to use Xcode and Interface builder for building your apps UI and connecting it to your controllers.
RayWenderlich.com is one of the best resources for ongoing learning for mac developers. They have detailed video tutorials, several books, as well numerous epic written tutorials in their tutorial section.
Apples WWDC videos are available to watch online.
Swift Development with Cocoa gives a good introductory overview of Cocoa development and covers both iOS and OS X development.
Swift is not a functional programming language. But it does provide some interesting features that facilitate programming in a somewhat functional style. If you are interested in learning more about functional programming in Swift I recommend the book Functional Programming in Swift.
Creating an Apple developer account gives you access to the apple developer portal (even without enrolling in one of the specific developer programs), which has lots of documentation on various frameworks for both platforms.
That’s it. Good luck.