Apple Mach-O Linker (Id) error

Got this error for the first time, I have looked around and cannot find a solution to help me, I have cleaned my build and also checked to make sure I am compiling for the latest firmware.

This happened after I tired implementing a reachability solution I found over here I imported the two reachability files (.m/.h) then added this code into the .m file and delared t in the . h of the reachability files

-(BOOL)reachable {
    Reachability*r =[Reachability reachabilityWithHostName:@"enbr.co.cc"];
    NetworkStatus internetStatus =[r currentReachabilityStatus];
    if(internetStatus ==NotReachable){
        return NO;
    }
    return YES;}

After that I called the function from both of my viwcontrollers viewwillappea开发者_运维技巧r methods like so..

- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];


    //-- Check Reachability START ---->
    Reachability *reach = [[Reachability alloc] init];

    if ([reach reachable]) {
            NSLog(@"Reachable");
    }
    else {
        NSLog(@"Not Reachable");
    }
     //-- Check Reachability END ---->
}

No errors were produced untill I tried to build and run in the simulator. This is the error I received :(

Ld /Users/imac/Library/Developer/Xcode/DerivedData/wizcode-ccyrqptvfsabmbahgxartbvxwurq/Build/Products/Debug-iphonesimulator/wizcode.app/wizcode normal i386 cd "/Users/imac/Documents/Iphone applications/wizsanCode/wizsanCode.5/wizcode" setenv MACOSX_DEPLOYMENT_TARGET 10.6 setenv PATH "/Developer/Platforms/iPhoneSimulator.platform/Developer/usr/bin:/Developer/usr/bin:/usr/bin:/bin:/usr/sbin:/sbin"

/Developer/Platforms/iPhoneSimulator.platform/Developer/usr/bin/llvm-gcc-4.2 -arch i386 -isysroot /Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator4.3.sdk -L/Users/imac/Library/Developer/Xcode/DerivedData/wizcode-ccyrqptvfsabmbahgxartbvxwurq/Build/Products/Debug-iphonesimulator -F/Users/imac/Library/Developer/Xcode/DerivedData/wizcode-ccyrqptvfsabmbahgxartbvxwurq/Build/Products/Debug-iphonesimulator -filelist /Users/imac/Library/Developer/Xcode/DerivedData/wizcode-ccyrqptvfsabmbahgxartbvxwurq/Build/Intermediates/wizcode.build/Debug-iphonesimulator/wizcode.build/Objects-normal/i386/wizcode.LinkFileList -mmacosx-version-min=10.6 -Xlinker -objc_abi_version -Xlinker 2 -lz -framework CoreGraphics -framework MobileCoreServices -framework SystemConfiguration -framework CFNetwork -framework UIKit -framework Foundation -o /Users/imac/Library/Developer/Xcode/DerivedData/wizcode-ccyrqptvfsabmbahgxartbvxwurq/Build/Products/Debug-iphonesimulator/wizcode.app/wizcode

ld: duplicate symbol _OBJC_IVAR_$_Reachability.reachabilityRef in /Users/imac/Library/Developer/Xcode/DerivedData/wizcode-ccyrqptvfsabmbahgxartbvxwurq/Build/Intermediates/wizcode.build/Debug-iphonesimulator/wizcode.build/Objects-normal/i386/Reachability-183E2D17A6B26176.o and /Users/imac/Library/Developer/Xcode/DerivedData/wizcode-ccyrqptvfsabmbahgxartbvxwurq/Build/Intermediates/wizcode.build/Debug-iphonesimulator/wizcode.build/Objects-normal/i386/Reachability-183E2D17A6B26176.o for architecture i386 collect2: ld returned 1 exit status Command /Developer/Platforms/iPhoneSimulator.platform/Developer/usr/bin/llvm-gcc-4.2 failed with exit code 1 ld: duplicate symbol _OBJC_IVAR_$_Reachability.reachabilityRef in /Users/imac/Library/Developer/Xcode/DerivedData/wizcode-ccyrqptvfsabmbahgxartbvxwurq/Build/Intermediates/wizcode.build/Debug-iphonesimulator/wizcode.build/Objects-normal/i386/Reachability-183E2D17A6B26176.o and /Users/imac/Library/Developer/Xcode/DerivedData/wizcode-ccyrqptvfsabmbahgxartbvxwurq/Build/Intermediates/wizcode.build/Debug-iphonesimulator/wizcode.build/Objects-normal/i386/Reachability-183E2D17A6B26176.o for architecture i386

Command /Developer/Platforms/iPhoneSimulator.platform/Developer/usr/bin/llvm-gcc-4.2 failed with exit code 1

So, the problem has been resolved.

What happened was when I imported the reachability files over into my build something funny was happening and somehow I deleted the reachability files that were already in my build being used by the "all seeing I" ASIHTTPRequest methods I was using for transporting my data... which messed everything up.

So long story short I replaced the files and everything is working fine and I also found out that ASIHTTPTequest is taking care of the reachability for me :) how cool is that.

Check if SystemConfiguration is linked properly. Anyway, clean up your code:

+ (BOOL)reachable {
    Reachability *r = [Reachability reachabilityWithHostName:@"enbr.co.cc"];
    NetworkStatus internetStatus = [r currentReachabilityStatus];
    return internetStatus != NotReachable;
}

And then just call [Reachability reachable] wherever you need. This also fixes a memory leak you have.

Just to add to this, it happened me after I regenerated managed subclasses and it didn't actually overwrite the existing ones but just made new duplicates. I just deleted both and regenerated and it was all good.

After modifying my core data model, I deleted all the (auto generated) NSManagedObjectModel subclasses, and created them again. Once they all were created, I dragged them to a Group folder in XCode... and got the spinning beachball for longer than usual.

The next time I tried to run, it failed with the "Mach-O-Linker" (Id) Error. After reading other responses, I figured it might have something to do with the NSMObj classes not being where expected. I deleted them, quit, opened, generated them, and put them in their customary group folder... and Viola! no Mach-O error.

I see that the problem is resolved, but I post this just to index it under the proper question. In my case, deleting and regenerating (via editor menu) the managed object subclasses fixed the issue.

Remove it then add it again. Works for me. :D

This happens with me when i am adding third party analytics framework in my project. When i check with the info of framework its not properly copied on disk. i download new framework and copied it into project and now there is no error.

I had this code in one of my UIViewController and removing it solved this bug. What a stupid and not-clear-at-all error message

NS_ENUM(NSInteger, Mode) {
    Assessments = 0,
    Onboarding
};

Make sure you are running YourApp.xcworkspace instead of .xcodeproj file. I did face the same issue when did run .xcodeproj file. Running .xcworkspace has solved the problem and the error has gone away.