Well, I'm not sure exactly what's under the hood, but I write Apple software, and I use a lot of the same NSXXX calls that have been in it since the dawn of OSX.
NextStep was a shell over FreeBSD. MacOS X was an evolution of NextStep.
Some time ago, I wrote a network driver for iOS, and used BSD sockets, accessed via standard C. I remember using the BSD manual, to figure out how to use them.
The NS calls behave the same now, as they did, back when OSX was new, and, at that time, MacOS was definitely UINX. iOS is a direct descendant of MacOS.
macOS is literally certified Unix. Apple still shells out for certification of their new releases, although I'm not sure what they're getting out of it given that macOS Server isn't a thing anymore.
iOS is arguably a subset, but whether it's Unix-like or not is a philosophical question depending on how you define the minimal set of features that'd make it one. It's certainly not Unix-like from the end user perspective.
NextStep was a shell over FreeBSD. MacOS X was an evolution of NextStep.
Some time ago, I wrote a network driver for iOS, and used BSD sockets, accessed via standard C. I remember using the BSD manual, to figure out how to use them.
The NS calls behave the same now, as they did, back when OSX was new, and, at that time, MacOS was definitely UINX. iOS is a direct descendant of MacOS.