“Undefined symbols for architecture arm64” on extension

Question

My app builds fine, but now I'm attempting to build for Archive, and I'm getting this error:

Undefined symbols for architecture arm64:
  "type metadata for (extension in TwIM):__ObjC.NSData.ImageType", referenced from:
      static TwIM.ImageCache.imagePath (imageURL : __ObjC.NSURL, imageType : (extension in TwIM):__ObjC.NSData.ImageType?) -> Swift.String? in ImageCache.o
      function signature specialization <Arg[0] = Owned To Guaranteed and Exploded> of static TwIM.ImageCache.imagePath (identifier : Swift.String, imageType : (extension in TwIM):__ObjC.NSData.ImageType?) -> Swift.String? in ImageCache.o
      function signature specialization <Arg[0] = Owned To Guaranteed and Exploded> of static TwIM.ImageCache.imageData (identifier : Swift.String, imageType : (extension in TwIM):__ObjC.NSData.ImageType?) -> __ObjC.NSData? in ImageCache.o
      function signature specialization <Arg[0] = Owned To Guaranteed and Exploded> of static TwIM.ImageCache.image (identifier : Swift.String, imageType : (extension in TwIM):__ObjC.NSData.ImageType?) -> Swift.AnyObject? in ImageCache.o
      function signature specialization <Arg[0] = Owned To Guaranteed, Arg[1] = Owned To Guaranteed and Exploded> of static TwIM.ImageCache.saveImage (imageData : __ObjC.NSData, identifier : Swift.String, imageType : (extension in TwIM):__ObjC.NSData.ImageType?) -> Swift.Bool in ImageCache.o
      function signature specialization <Arg[0] = Owned To Guaranteed and Exploded> of static TwIM.ImageCache.removeImage (identifier : Swift.String, imageType : (extension in TwIM):__ObjC.NSData.ImageType?) -> () in ImageCache.o
ld: symbol(s) not found for architecture arm64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

What it's referring to is an extension I have on NSData, which includes an enum:

extension NSData {
  enum ImageType: String {
    case jpg = "jpg"
    case png = "png"
    case gif = "gif"
  }
}

I don't know why this would be causing an issue. I've cleaned, and cleared derived data as some people have suggested.

Answer 1

Which Xcode and which Swift version do you use?

I first discovered this error message with Xcode 8 and Swift 3 beta 6. I had a look on what I imported but it was only Cocoa for all files. There were several errors of this kind, almost all belonging to a function, which was very large. The error only happens, if Global-Module-Optimization is selected, regardless if running or archiving.

So I divided this function in 6 smaller parts to look, which one was causing the problem. After making the function smaller, only two errors of this kind stayed. So I think it is a linker/optimizer-Problem in my case, because the code is the same, only divided in several small functions.

Please try to select Single-File-Optimization for Release and try to Archive. Does the error come again or are you successfull?

I guess, this will be not a problem in the final release.

Answer 2

I had this problem too. And I solved this with following operations: 1. Go to build setting. 2. Search for enable testablility. 2. Set No for Debug.

Answer 3

Try getting rid of the enum. That's what fixed it for me. Maybe there's a problem with enums in extensions.