Undefined symbols for architecture arm64

Question

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         


        

Answer 1

Given an iPhone 5s and not yet having received a 64 bit version of a third party library, I had to go back to 32 bit mode with the latest Xcode (prior to 5.1 it didn't complain).

I fixed this by deleting arm64 from the Valid Architectures list and then setting Build Active Architecture Only to NO. It seems to me this makes more sense than the other way around as shown above. I'm posting in case other people couldn't get any of the above solutions to work for them.