How can I switch to Swift 4.0 in Xcode 9.3?

问题

It seems like I have only options to go to 3.3, or unspecified:

Can I switch to 4.0 somehow?

回答1:

Make sure you have updated xCode then under Build Settings, check the drop down options for Swift Compiler - Language.

Furthermore, You can download Xcode 8.x and 9.x from Apple Download Portal, if you've premium developer account (apple id). You can install & work with both Xcode 9 and Xcode 8.x in single (mac) system. (Make sure you've Command Line Tools supporting both version of Xcode, to work with terminal)

回答2:

I was able to install swift 4.0 in XCode 10 with solution from here "Switching Swift Versions inside Xcode using Toolchains".

But in the end this did not help. I stuck on error:

< unknown>:0: error: unknown argument: '-enable-batch-mode'

Even disabling not helped. I got:

< unknown>:0: error: unknown argument: '-disable-batch-mode'

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"Switching Swift Versions inside Xcode using Toolchains" shortly:

1. Download desired toolchain, and click to install.
2. Select new toolchain in XCode Preferences.
   1. Select here:
   2. Result here:
3. Use desired swift, beware caveats.

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Another related: material.

来源：https://stackoverflow.com/questions/49667188/how-can-i-switch-to-swift-4-0-in-xcode-9-3