New Features in Swift 4

Faster, easier to use Strings that retain Unicode correctness and add support for creating, using and managing substrings

Smart key paths for type-safe, efficient, extensible key value coding for Swift types

Enhancements to creating and manipulating Dictionary and Set types

Extends support of archival and serialization to struct and enum types and enables type-safety for serializing to external formats such as JSON and plist

Enforced exclusive access to memory