swift-corelibs-foundation | Foundation Project , providing core utilities | Web Framework library

I don't think there is such formatter in Swift but you can subclass NumberFormatter and create your own CompactNumberFormatter if needed:

You will have to implement your own solution, but it is not hard. One way to go would be to create two dictionaries where the key will be the Locale identifier and the value the translation:

This is caused by a recent move of networking related objects into a new FoundationNetworking module. The new module does not exists on Darwin, so one must use preprocessor commands to make code work on all supported platforms:

It would appear to be a REPL issue and existed in 11.0, too. But if you print(testUrl1), you’ll see it really is set.

First, and most importantly, swift-corelibs-foundation is not the Foundation from iOS and macOS:

This project, swift-corelibs-foundation, provides an implementation of the Foundation API for platforms where there is no Objective-C runtime. On macOS, iOS, and other Apple platforms, apps should use the Foundation that comes with the operating system. Our goal is for the API in this project to match the OS-provided Foundation and abstract away the exact underlying platform as much as possible.

Next, your test case does not carefully test NSCache. Your Data objects could be stored on the autorelease pool and not released. In this case that's not true, but it's the kind of thing you need to be very careful about when testing memory usage.

That said, I can't reproduce your issue. When I put this in an iOS app and run it on iOS 12, I see the kind of behavior you're probably expecting:

Big run-up in memory usage to ~1GB, at which point the cache is dumped as expected.

I also wasn't able to easily reproduce it on macOS (but I wasn't patient enough to let it crash, so it's possible it eventually would). You'll need to give a more precise example of where this crashes unexpectedly in order to diagnose why.

I think you are right assuming that request is nil, when the error occurs. A similar problem is described here.
Since URLRequest.swift, as defined in apple/swift-corelibs-foundation that your cited will definitively crash if request is nil, one cannot use it in this situation.
One alternative is definitively to use KVO, since func value(forKey key: String) -> Any? can return nil values, see here.
However, you can only use it, if the object, in which the function is called, adopted the NSKeyValueCoding protocol, which is ensured if the object is a subclass of NSObject, which I cannot tell from your code fragment.
But since you suggested this already in your question, did you try it?

I downloaded the swift development toolchain and added it in xcode. I can now successfully build and run tests. Thanks Hamish :)

As of writing (August 8th, 2017), this currently is not possible with any version of Swift (3 or 4).

Without a header declaration, clang isn't sure how to map something in Swift back to C. @_silgen_name and @_cdecl work on functions, but not for variables.

This was confirmed by Jordan Rose, a Swift compiler engineer at Apple on Twitter.

tl;dr:

anything but func is hard.