Swift 4.0 is now available. It’s a major upgrade to Apple’s Swift, the three-year old successor to the Objective-C language used for MacOS and iOS application development.
The Swift 4 upgrade enhances the Swift Package Manager and provides new compatibility modes for developers. Apple said Swift 4 also makes Swift more stable and improves its standard library. Swift 4 is largely source-compatible with Swift 3 and ships as part of Apple’s Xcode 9 IDE.