Today I started working on updating Apport code from Swift 2 to Swift 4. So I got everything ready, made a fresh cup of coffee and opened the project workspace in Xcode 9. And then I got this message:
I have to convert the project to Swift 3 first in Xcode 8 and then convert once again to Swift 4 in Xcode 9.
So I need both Xcode 8 and Xcode 9 installed, and here is how that can be done:
Download Xcode 8.3.3 from Apple Developer Downloads. You will receive a file named Xcode8.3.3.xip which is a digitally signed zip file.
Expand the xip file. It will be expanded to
Selecting Xcode version
Switch to Xcode 8
sudo xcode-select --switch /Applications/Xcode8.app
Switch to Xcode 9
sudo xcode-select --switch /Applications/Xcode.app
Print version that is selected