How to fix “SWIFT_VERSION '3.0' is unsupported, supported versions are: 4.0, 4.2, 5.0” error in Xcode 10.2?

问题

I'm trying to run downloaded from app, try to open in Xcode and have an error:

" Showing Recent Messages
:-1: SWIFT_VERSION '3.0' is unsupported, supported versions are: 4.0, 4.2, 5.0. (in target 'SimpleWeather')"

回答1:

Select the target 'SimpleWeather' in the project and change language version Target->build setting -> Swift compiler language -> select 5, 4.2 etc

回答2:

******** Easiest way: **********

1.Click on PODs in the left column.

2.In the centre column select the pod you want, then navigate to "build settings" in the top right panel.

3.Then search "Swift Language Version" and change to a known version.

回答3:

For Xcode 10.1, select your Pods File

-> Go to Build Settings -> Choose your Pod -> Search "Swift" -> Navigate to "Swift Language version" -> Set to desired language version.

回答4:

I followed the instructions on this page and the error didn't resolve. Finally, went into

$ vim MyProject.xcodeproj/project.pbxproj

and found two instances where

SWIFT_VERSION = 3.0;

was still being referenced. I changed those to 5.0 and the error was gone. Not sure why those two were still there.

回答5:

It seems that the app might have an old Swift version code like Swift 3.0 in your case. In the release of Xcode version 10.2 has launched Swift 5.0 version. Xcode 10.2 does not support compiler for Swift 3.0 version. You can change compiler from Build Settings -> Swift Compiler - Language -> Swift Language Version -> Change it to Swift 5. If your code is compatible with that language version then it will run the code without error.

However, the Swift 3 compatibility mode will not be supported in the Swift 5 compiler. Swift 4.2 is the last release of Swift to support Swift 3 mode. There are important changes to both the surface of the language and the interior of its implementation in the releases following Swift 3 that will be the basis of future (and lasting) source and binary stability.

Refer below link for more details. https://developer.apple.com/documentation/xcode_release_notes/xcode_10_2_release_notes/swift_5_release_notes_for_xcode_10_2

If you really wish to run the app which has older Swift version code than you must have to use an older version of Xcode. You can use Xcode version 10.1, it's compiler having support for Swift 3.0 version.

Another alternative way is to migrate your old Swift code to the new version of the Swift version. You can migrate you Swift 3.0 to Swift 4.0 in Xcode 10.1 version.

For migration guide refer to this https://swift.org/migration-guide-swift4/

回答6:

select pod like as per image and change swift language version this can save you one day

回答7:

I came across this issue while developing a Cocoapod. I had an old .swift-version file in my repo that specified Swift 3.0.

Running pod lib lint --verbose led me to this helpful response:

Please remove the .swift-version file which is now deprecated and only use the swift_version attribute within your podspec.

I deleted the file and added spec.swift_version = '5.0' to my podspec file to fix the problem.

回答8:

1. Select project
2. Select Build SettingTab
3. Select Swift Compiler language Option

回答9:

1. Check this out:
   1. Click on Project name
   2. Click target
   3. Click on Build setting
   4. At the Swift Language Version: Choose Swift 4

回答10:

1) change pod's version on podfile (because library wrote old swift version )

2) "pod install" on terminal

来源：https://stackoverflow.com/questions/55366024/how-to-fix-swift-version-3-0-is-unsupported-supported-versions-are-4-0-4-2