Swift Everywhere: Using Interoperability to Build on Windows

Swift’s deliberate design choices over the years has resulted in a language that showcases how flexibility and compatibility does not need to come at the cost of usability. One of these design choices was Swift’s focus on native interoperability with other languages. The flexibility that this enables makes it a joy to build rich, native experiences in Swift across a variety of environments.

→ swift.org/blog/swift-everywhere-windows-interop/

Swift’s design emphasises seamless interoperability with other languages, particularly C and C++, by embedding clang to avoid the performance and boilerplate costs of traditional C-based Foreign Function Interfaces (FFI) like libffi.

This enables direct access to the Windows API, primarily defined in C, through clang modules like WinSDK, with Swift overlays for a more idiomatic experience, and Swift 5.9’s C++ interoperability extends this to C++ APIs, such as those in the Windows SDK and libraries like Firebase.

The Component Object Model (COM), a prevalent Windows mechanism for inter-process communication, aligns well with Swift’s class types, allowing Swift to interact with COM interfaces via C or emerging C++ interoperability, with projects like Swift/COM and DXSample demonstrating practical applications.

Future enhancements, including potential COM-specific language annotations and integration with distributed actors for Distributed COM (DCOM), aim to reduce boilerplate, improve memory safety with ARC, and enable robust, cross-platform applications leveraging Swift’s interoperability tools.