Xcode 9 - 链接器命令失败，退出代码为1

Question

While compiling the application getting as following error

" compiled with older version of Swift language (3.0) than previous files (4.0) file "

Could you please help me?

Answer 1

Use the xcworkspace to build instead of the xcproject?

This usually happens when using Cocoapods and you are building from the xcproject which doesn't know about the cocoapod libraries.

Answer 2

Delete the derived data and do a clean build.

And if you are building a framework, make sure you've selected Generic IOS Device while building or set the Build for Active Architecture only as true in Build Settings .

Answer 3

I think this happens because you changed your app name or maybe the target

look to solve this problem see your target in Podfile

and then come back to your xcode in the targets select your target app and in linked Frameworks and Libraries (the last one down) see if there's any pods with light color and a strange name than your target in the podfile and remove it using the minus button down .

Answer 4

I'd rather fix the specific problem, but if none of the other answers worked a full reset can solve it. If you are getting this error and you are also getting error readouts that refer to "duplicate symbol files", AND all other efforts have failed, then a full reset could work for you.

What worked for me:

1. Read the error report to identify the repo that supposedly contains duplicate files.
2. Drag repo to the trash.
3. re-clone your repo.
4. set up your repo with correct remote tracking. git remote add <url.git> , or git remote set-url <url.git>

This absolutely worked for me. In my case for some elusive reason, when I ran git pull upstream develop for a local dependency, git would pull in/generate duplicate files from multiple commits.

After following the above steps, the issue went away and git pull upstream develop was no longer pulling from multiple commits at once. Perhaps there was a weird git cache for my repo.

Answer 5

I am probably late for you, but for future devs in problems...

If you have been manipulating the podfile or creating new targets or maybe changing the name of any of them, check that in build phases options your just have correct pod framework for the name of the targets.

Answer 6

I had the two copies of files in the codebase. Deleting one copy helped code to build successfully

Answer 7

如果你有pod第一个清理项目并关闭Xcode然后打开终端并转到Project的文件夹然后pod update打开项目并在我的案例工作中运行！

Answer 8

I fixed this problem today by running the app in the simulator using the target associated with the bundle file named in the Build Settings-->Bundle Loader setting of the test target. Previously I had deleted my derived data folder while working on a different target that has a different Product Name than the one associated with the test target bundle file. Rerunning the app in the simulator must have recreated the bundle file in the derived data folder that the test target is looking for and then my tests started running fine.