Xcode: How can i show which version of swift is used in Xcode?

If you want to look up, which version of swift you are using in Xcode, use the following command in your Terminal:

xcrun swift -version

The output look like this

Apple Swift version 3.0.2 (swiftlang-800.0.63 clang-800.0.42.1)
Target: x86_64-apple-macosx10.9

An alternative way is

$ swift --version
Apple Swift version 3.0.2 (swiftlang-800.0.63 clang-800.0.42.1)
Target: x86_64-apple-macosx10.9

Hope this helps!
Patrick