It gives errors when using Swift Static library with Objective-C project
I've got the same error on my demo project when added first Swift file in my pod compiled as static library. For me solution was simple - just added empty Swift file to my demo project which was previously in Objective-C only. This solved all linker errors.
An update to Alex's answer:
In my case it was a React-Native project after adding a Swift Pods library. Maybe just the step 2 can work:
- Adding a new Swift file and a Brigde header:
1) File -> New -> File
2) Select Swift File 
3) Confirm Create Bridging Header 
- Go to
Build Settingsand setAlways Embed Swift Standard LibrariestoYES
This answer worked for me: Add $(TOOLCHAIN_DIR)/usr/lib/swift/$(PLATFORM_NAME) to the library search paths.