Undefined symbols for architecture x86 64 on Xcode 6 1

Question

All of a sudden Xcode threw me this error at compilation time    Undefined symbols for architecture x86 64    OBJC CLASS   Format   referenced from   objc-class-ref in WOExerciseListViewController o ld  symbol s  not found for architecture x86 64 clang  error  linker command failed with exit code 1  use -v to see invocation    After doing some research  I may understand that a library I m using is not compatible with 64 bit version  But this is very strange since I ve been working with the same libraries for at least a week without having a single compilation problem during that time  The two libraries are just composed of a bunch of classes  and when I removed them from my project I got the same issue  Since I have never created libraries myself  I have no idea how I can find wether the ones I m using are compatible with 64 bit     I also tried the following changes for architectures under the target panel      added   ARCHS STANDARD INCLUDING 64 BIT  to the Architectures build active architecture only -  set to  NO   for  valid architectures  -  set to arm64  armv7 and armv7s deleted the DerivedData folder and its contents  cleaned and built again    But none of these changes work  Please  does someone have a clue on this   Thanks

User · Answer

I just had the exact same error  and solved it by restarting xcode   For me the issue occurred after an svn update  the file in question was added to the projects folder  but it never appeared in xcode 9 3 1      until I restarted it

User · Answer

Yes  I think the library you are using is not compatible with 64 bit version but you can solve the problem -   Just navigate to Build Settings Architectures  amp  replace   ARCHS STANDARD  to   ARCHS STANDARD 32 BIT    So that your xcode build your project with 32 bit supported version

User · Answer

It turned out I forgot to write my  implementation part

User · Answer

Make sure the WOExerciseListViewController is a Target Member  that worked for me

User · Answer

I just had this error when I opened a  quite  old project  created in Xcode 4 ish  in Xcode 6 4  While the linked Frameworks were visible in the Project sidebar  I overlooked that there were no linked libraries in the Target Build Phases tab  Once I fixed that  it compiled fine

User · Answer

I solved the same issue by going to Xcode Build Settings and in Architectures  I changed  the Xcode 6 1 1 standard architecture to -    ARCHS STANDARD 32 BIT

User · Answer

I solved the problem by deleting reference to the file and adding it again in project  In my case it works

User · Answer

Same error when I copied pasted a class and forgot to rename it in  m file

User · Answer

Check if that file is included in Build Phases -  Compiled Sources

User · Answer

Apparently  your class  Format  is involved in the problem  Check your declaration of this class  especially if you did it inside another class you probably forgot the  implementation or something similar

User · Answer

I simply wasn t linking the libraries in the  Link Binary with Libraries  section

User · Answer

Delete the   ARCHS STANDARD  and add the   ARCHS STANDARD 32 BIT

User · Answer

this setting worked for me    Architectures   ARCHS STANDARD 32 BIT  Build Active Architecture Only YES      Valid Architectures armv6 armv7 armv7s arm64

[ios] Undefined symbols for architecture x86_64 on Xcode 6.1

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