Undefined symbols for architecture x86_64 in Xcode

Question

I updated FirebaseUI to the newest version, and that updated TwitterCore 3.0.0 (was 2.8.0), ever since I get this compiler error in Xcode:

Undefined symbols for architecture x86_64:
  "_TWTRIdentifierForAdvertising", referenced from:
      +[TWTRCardConfiguration deviceID] in TwitterKit(TWTRCardConfiguration.o)
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

I currently reverted back to the previous version of TwitterCore even though it wasn't explicitly written in my Podfile. I wrote pod 'TwitterCore', '~>2.8.0'

Answer 1

I noticed in the Firebase DatabaseExample podfile included with quickstart-ios that 'FirebaseUI' was renamed 'FirebaseUI/Database'. I added it to the podfile with the correct name and all appears to be ok.

Answer 2

In my case it was just commented out this :

# pod 'FirebaseUI/Twitter'