The Swift programming language was first introduced in June 2014 at Apple’s Worldwide Developers Conference (WWDC). Swift was a surprise to everyone: Apple had managed to develop an entire language (as well as all the supporting libraries, developer tools, and documentation) and make it work seamlessly with the existing Objective-C language. And on top of that, it was a really good “1.0” language.
In June 2015, Apple announced Swift 2.0, improving the performance of the language, adding a collection of new features, and making the Cocoa and Cocoa Touch platform APIs more Swift-like in style. Swift was open sourced on December 3, 2015, and is now as much a community-run project as an Apple-run one. We can expect Swift to evolve over time, in line with the developments in the Swift Open Source project.
Xcode supports having multiple versions of the Swift language installed. You might have a different version of the language if, for example, you’ve downloaded a copy of Swift from the open source project. For information on how to get a copy and use it in Xcode, go to the Swift project’s Download page.
This book covers Swift 3, which was released in September 13, 2016. The 3.0 release was a very big deal in the Swift community and included numerous changes to the language as well as to the standard library. With the release of Swift 3, future changes to the language aim to be smaller in scope and more backward compatible.
If you have older Swift ...