I am getting a Apple Mach-O Linker Error everytime I import a file from CocoaPods.
Undefined symbols for architecture arm64: \"_OBJC_CLASS_$_FBSession\", r
If the architecture and linker settings look good, check your h files. My issue was the same error, but I had restructured the h files and I removed an extern statement. Other m files were using that variable, causing the linker error.