This morning, I discovered that Swift uses a different cross platform approach to Objective C. To determine the OS for type aliasing, use  os() and pass it either OSX or iOS, as in the following example:

// OSX, iOS
#if os(iOS)
    typealias View = UIView
#else
    typealias View = NSView
#endif

Once defined, the following code ran on both iOS and OS X. It compiled without incident and correctly reported the correct class of  var myView = View() when I ran println("\(myView.description)") In addition to OS testing, you can check whether your code is running on the simulator or on-device.  The following code all seemed to behave properly in my tests.

// x86_64, arm, arm64, i386
#if os(iOS)
    println("iOS")

    #if arch(i386) || arch(x86_64)
        println("Simulator")
    #else
        #if arch(arm)
            println("Device (arm)")
        #else
            println("Device (arm64)")
        #endif
    #endif
#else
    println("OS X")
#endif

I should mention that compiling to device had several issues. First, Xcode gave me a bit of a hard time about code signing, which I bypassed by linking the codesign_allocate from Xcode 5 (/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/codesign_allocate) to /usr/bin. I also had to hand-update the developer settings for development/distribution.

Second, I could not get anything to run with my iOS 8 device. This is apparently a known problem.  I ended up restoring the thing, and it still doesn’t work. So I just put it aside for now and am compiling for the moment to my primary iOS 7 device, which is fine for early tests, but not great for new APIs. I’ll update if I get the #$@%ing device working. (And no, rebooting everything multiple times didn’t work, nor did disconnect/reconnect. It’s really chicken-entrails-time here.)

Final pro tip. In the Devices organizer in new Xcode, right-click the device and choose Show Provisioning Profiles to access them. Here is also where you can click to rename your device, and because it’s a standard text field, it will even offer to spell-correct your device name with hilarious suggestions.