[richard_todd]

Whenever I've looked at examples on Swift on Linux in the past, the code always started with (hazy memory here) `use glibc` or similar, whereas the macOS version used a different library. So for example even just to produce a random number you had to use two completely different library functions imported with completely different names. All that to say: it's always felt to me like "cross-platform" for Swift means "the same syntax on a completely different platform." Has that changed, or will basic functionality on windows require a third completely different set of libraries?

[Disparallel]

It depends on what you're doing. Swift Foundation is cross platform for Windows/Linux/macOS and exposes apis for things like file systems, paths, process creation with the caveat that what a "Thread" is or what it means if a file is executable is a little different between platforms. If you're writing a cli tool you should be able stay mostly within the Swift stdlib and Foundation and that'll work on all platforms. As more libraries are ported to Windows (e.g. hopefully swift-nio), that should become more and more the case.

Where this isn't the case would be if performance mattered, some of Foundation system api implementations (at least, the Windows ones) can be a little inefficient since the Foundation api model and the Windows way of doing things doesn't always match and the Windows implementation has to do extra work to match the semantics.

Another would be UI wise, I haven't heard of plans for Apple to open source SwiftUI. Though since Swift can call into the native platform apis, it's quite possible to write a (perhaps not as slick) alternative.

[richard_todd]

Sounds like things have improved in the last couple years, thanks for the information. If they get to the point where a basic database-querying microservice will usually compile on all three platforms, I could imagine a lot more server-side interest in the language. Who knows?

[skohan]

FWIW it's already viable to use Swift in the micro-service use-case. If you're running logic inside containers it's trivial to get a Swift service up and running.

[ken]

Random numbers, at least, are now part of the standard library.

As for the rest, it depends on what you consider "basic functionality". AppKit/UIKit is probably never going to be ported.

[wlesieutre]

Probably UIKit versus Foundation. UIKit is iOS/Mac only and I think indirectly includes Foundation, which is where the essential non-UI APIs are.

All this really means is you don’t get the iOS UI tools for your Windows and Linux projects.

[pasta1212]

UIKit is iOS only, not Mac

[wlesieutre]

https://developer.apple.com/documentation/uikit/mac_catalyst