Diego Freniche Diego Freniche - 7 months ago 45
Swift Question

How can I programmatically find Swift's version?

I know I can find the version of Swift I'm running right now reverting to a Terminal and typing:

xcrun swift --version
Swift version 1.1 (swift-600.0.57.4)
Target: x86_64-apple-darwin13.4.0


Also, I've been reading about the Preprocessor Macros in Swift, but no luck finding a Swift version constant.

As Swift 1.2 approaches it will be nice to flag old code that only runs on Swift 1.1 (Xcode up to 6.2) or new code that needs Xcode 6.3 (Swift 1.2)

Note: I can also use system() to do something like:

system("xcrun swift --version | grep version > somefile.txt")


Then open somefile.txt, but rather prefer some simpler solution

Answer

Finally got a workaround to do this. I'm using the constants prefixed with __ you can observe in your Playground. This would have been easier with some level of reflection, but...

__IPHONE_OS_VERSION_MAX_ALLOWED is 80200, meaning __IPHONE_8_2 for Xcode 6.2 (Swift 1.1) but its value is 80300 (__IPHONE_8_3) in Xcode 6.3 (Swift 1.2)

func isSwift12() -> Bool {
  return __IPHONE_OS_VERSION_MAX_ALLOWED == 80300
}

isSwift12()

So now in your library you can fail fast and tell your user Swift's version is not correct using this:

assert(isSwift12(), "Need Swift 12")

Swift will give you a nice:

assertion failed: Need Swift 12: file , line 20

UPDATE WWDC 2015 - Swift 2.0

As stated in Apple's Swift blog, in Swift 2.0 we have #available blocks to check for certain OS versions in our code. An example should be:

if #available(OSX 10.11, *) {
    monochromeFilter!.setValue(CIColor(red: 0.5, green: 0.5, blue: 0.5), forKey:kCIInputColorKey)
} else {
    // Fallback on earlier versions
}