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.
What’s new in Swift 4’s package manager
Swift Package Manager, which debuted in Swift 3, is tool for distributing code. It is integrated with the Swift build system to automate processes including downloading, compiling, and linking of dependencies. Improvements in Swift 4’s package manager include: