The Big Nerd Ranch Guide. M. Mathias, J. Gallagher

 Through the authors' carefully constructed explanations and examples, you will develop an understanding of Swift grammar and the elements of effective Swift style. Written for Swift 2.0, the book is also compatible with Swift 2.1. You will also learn how to navigate Xcode 7 and get the most out of Apple's documentation. Throughout the book, the authors share their insights into Swift to ensure that you understand the hows and whys of Swift and can put that understanding to use in different contexts.