Swift is a powerful and intuitive programming language for macOS, iOS, watchOS and tvOS. Writing Swift code is interactive and fun, the syntax is concise yet expressive, and Swift includes modern features developers love. Swift code is safe by design, yet also produces software that runs lightning-fast. In Swift Playgrounds you create small programs called “playgrounds” that instantly show the results of the code that you write. A single line of code can make amazing things happen. Interactive lessons teach key coding concepts, and additional challenges and templates encourage you to explore code in exciting new ways and to create something completely unique.
Apple intended Swift to support many core concepts associated with Objective-C, notably dynamic dispatch, widespread late binding, extensible programming and similar features, but "safer" (easier to catch software bugs); Swift has features addressing some common programming errors like null pointers and provides syntactic sugar to help avoid the pyramid of doom. Swift supports the concept of protocol extensibility, an extensibility system that can be applied to types, structs and classes, which Apple promotes as a real change in programming paradigms they term "protocol-oriented programming". Swift was introduced at Apple's 2014 Worldwide Developers Conference (WWDC). It underwent an upgrade to version 1.2 during 2014 and a more major upgrade to Swift 2 at WWDC 2015.