symbol(s) not found for architecture i386

Question

When trying to compile with Xcode, I am getting the following error:

  **Ld /Users/doronkatz/Library/Developer/Xcode/DerivedData/iKosher-bphnihrngmqtkqfgievrrumzmyce/Build/Products/Debug-iphonesimulator/iKosher.app/iKosher normal i386
    cd /Users/doronkatz/Sites/xCode/iKosher
    setenv MACOSX_DEPLOYMENT_TARGET 10.6
    setenv PATH "/Xcode4/Platforms/iPhoneSimulator.platform/Developer/usr/bin:/Xcode4/usr/bin:/usr/bin:/bin:/usr/sbin:/sbin"
    /Xcode4/Platforms/iPhoneSimulator.platform/Developer/usr/bin/gcc-4.2 -arch i386 -isysroot /Xcode4/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator4.2.sdk -L/Users/doronkatz/Library/Developer/Xcode/DerivedData/iKosher-bphnihrngmqtkqfgievrrumzmyce/Build/Products/Debug-iphonesimulator -L/Users/doronkatz/Sites/xCode/iKosher -F/Users/doronkatz/Library/Developer/Xcode/DerivedData/iKosher-bphnihrngmqtkqfgievrrumzmyce/Build/Products/Debug-iphonesimulator -filelist /Users/doronkatz/Library/Developer/Xcode/DerivedData/iKosher-bphnihrngmqtkqfgievrrumzmyce/Build/Intermediates/iKosher.build/Debug-iphonesimulator/iKosher.build/Objects-normal/i386/iKosher.LinkFileList -mmacosx-version-min=10.6 -all_load -ObjC -Xlinker -objc_abi_version -Xlinker 2 -lz -framework Security -framework CFNetwork -framework CoreData -framework Foundation -framework UIKit -framework CoreGraphics -framework QuartzCore -o /Users/doronkatz/Library/Developer/Xcode/DerivedData/iKosher-bphnihrngmqtkqfgievrrumzmyce/Build/Products/Debug-iphonesimulator/iKosher.app/iKosher

Undefined symbols for architecture i386:
  "_UTTypeCreatePreferredIdentifierForTag", referenced from:
      +[ASIHTTPRequest mimeTypeForFileAtPath:] in ASIHTTPRequest.o
  "_UTTypeCopyPreferredTagWithClass", referenced from:
      +[ASIHTTPRequest mimeTypeForFileAtPath:] in ASIHTTPRequest.o
  "_kUTTagClassMIMEType", referenced from:
      +[ASIHTTPRequest mimeTypeForFileAtPath:] in ASIHTTPRequest.o
  "_kUTTagClassFilenameExtension", referenced from:
      +[ASIHTTPRequest mimeTypeForFileAtPath:] in ASIHTTPRequest.o
  "_SCNetworkReachabilitySetCallback", referenced from:
      -[Reachability startNotifier] in Reachability.o
  "_SCNetworkReachabilityScheduleWithRunLoop", referenced from:
      -[Reachability startNotifier] in Reachability.o
  "_SCNetworkReachabilityUnscheduleFromRunLoop", referenced from:
      -[Reachability stopNotifier] in Reachability.o
  "_SCNetworkReachabilityCreateWithName", referenced from:
      +[Reachability reachabilityWithHostName:] in Reachability.o
  "_SCNetworkReachabilityCreateWithAddress", referenced from:
      +[Reachability reachabilityWithAddress:] in Reachability.o
  "_SCNetworkReachabilityGetFlags", referenced from:
      -[Reachability currentReachabilityStatus] in Reachability.o
      -[Reachability isReachable] in Reachability.o
      -[Reachability isConnectionRequired] in Reachability.o
      -[Reachability isConnectionOnDemand] in Reachability.o
      -[Reachability isInterventionRequired] in Reachability.o
      -[Reachability isReachableViaWWAN] in Reachability.o
      -[Reachability isReachableViaWiFi] in Reachability.o
      ...
ld: symbol(s) not found for architecture i386
collect2: ld returned 1 exit status**

Not sure what it means.

Answer 1

If you get this sort of thing appearing suddenly, it usually means the project is missing some frameworks it needs. Libraries and dependent projects can require frameworks, so if you've added one recently then that can cause this error.

To add frameworks, right click on the project name in the project view, select Add, then select Existing frameworks... from the list. Then find the framework with the symbols you're missing.

As to how you find which frameworks you need, I've found using google the easiest, though you could probably use the Xcode help search too. Search for one of the symbols, doing your best to work out the unmangled name (e.g., SCNetworkReachabilityGetFlags), and then the first documentation link you find at developer.apple.com is often the right one. You usually don't have to hunt very far. In this case, that's this page:

https://developer.apple.com/documentation/systemconfiguration/scnetworkreachability-g7d

Then at the top of the page, it tells you which framework to use, SystemConfiguration in this case. So add that to the project, and compile again.

Then just keep doing this until it works...

Edit: I've never used the simulator, but this is what you do on the device - I assume it's the same...