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?
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.
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.
.podspecs I get this issue.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 .
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:
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.
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.