问题
For instance, I would play around Swift 4.2, but I don't want to use Xcode 10 beta version, I have Xcode 9.4.1.
I wonder if there is any way do it, is it possible?
回答1:
I figured it out that Yes it is possible. You can achieve it by installing the latest Snapshot:
Development Snapshots are prebuilt binaries that are automatically created from mainline development branches.
https://swift.org/download/#snapshots
Snapshot is a toolchain that you can install into Xcode which contains the latest compiler, leading to let you able to build your app on the latest tools.
How to setup a snapshot into Xcode?
1- Download the latest snapshot (Xcode) from Swift website.
2- Install the downloaded snapshot .pkg file.
3- Run Xcode and then go to: Xcode -> Toolchains -> Manage toolchains.
4- After selecting "Components" - "Toolchains" options, you should see:
Select "Swift Developer Snapshot" and thats it! You might need to reset Xcode after doing the above steps.
Reminder: You should reselect "Xcode 8.3.3" option after done playing around Swift 4, as mentioned in Swift - Using Downloads section:
To submit to the App Store you must build your app using the version of Swift that comes included within Xcode.
回答2:
If all you want to do is play around with Swift 4, you could also use the IBM Swift Sandbox which always has the most recent snapshot.
回答3:
Although it is not directly from the Xcode, you could also use the Iswift which should has the latest swift version (latest snapshot).
来源：https://stackoverflow.com/questions/44884571/is-it-possible-to-compile-latest-swift-version-on-older-xcode