That&#x27;s where Objective C bridging happens.  That&#x27;s irrelevant on Linux or Android, since there&#x27;s no Obj-C runtime.<p>OSS Foundation (which is composed of pure Swift code, plus the plain C CoreFoundation which is also open) implements bridging between Swift types and Foundation types itself--  see (for example) the Array extension for bridging to NSArray at [1].  That code&#x27;s what will (again, eventually) ship on Linux and presumably on Android, because it provides compatibility support for Swift libraries originally targeted to Apple platforms and fills out certain core functionality that&#x27;s not part of Swift&#x27;s stdlib (networking being a big one).  This work is still ongoing and, if one were to try to actually use it right now, you&#x27;d run into lots of bits that aren&#x27;t implemented yet.<p>[1] <a href="https:&#x2F;&#x2F;github.com&#x2F;apple&#x2F;swift-corelibs-foundation&#x2F;blob&#x2F;master&#x2F;Foundation&#x2F;NSArray.swift#L12" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;apple&#x2F;swift-corelibs-foundation&#x2F;blob&#x2F;mast...</a>