How to check the Swift version at compile time

Paul Hudson    September 15th 2016    @twostraws

Swift 2.2 introduced a new #if swift build configuration option, which lets you compile certain code only if a specific version of the Swift compiler is detected. This is particularly useful for libraries that need to support multiple incompatible versions of Swift at the same time, because only one version of their code will ever be compiled.

In the example below, the print() code will be compiled, but the capital letter text will be completely ignored – but only because we're using a Swift 2.2 compiler:

#if swift(>=2.2)
print("Running Swift 2.2 or later")
#else
THIS WILL COMPILE JUST FINE IF YOU'RE
USING A SWIFT 2.2 COMPILER BECAUSE
THIS BIT IS COMPLETELY IGNORED!
#endif

Available from iOS 7.0

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