build failed with ld duplicate symbol OBJC CLASS Algebra5FirstViewController

Question

I am getting this error suddenly when running my app via iPhone simulator      clang  error  linker command failed with exit code 1  use -v to see   invocation        ld  duplicate symbol  OBJC CLASS   Algebra5FirstViewController in       Algebra5-anwcuftojtxtgkfootneeeqhwztj Build Intermediates Algebra5 build Debug-iphonesimulator Algebra5 build Objects-normal i386 ExercisesViewController o   and        Algebra5-anwcuftojtxtgkfootneeeqhwztj Build Intermediates Algebra5 build Debug-iphonesimulator PSLE   Algebra5 build Objects-normal i386 PSLE Algebra5FirstViewController o   for architecture i386   What is it all about

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I got this same issue when working with Bolts framework  It turns out that when Bolts gets corrupted  no amount of re-importing will fix the issue  I had to go back to the original download file and reimport it completely from scratch  This fixed it right away  It was such a weird issue that it took me forever to figure it out    hopefully this tip will spare some of you from the same frustrations

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I was getting similar error and I got it resolved this way      Try to set Build Active Architecture Only to NO for  Pods  project and   your app s target

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I got a similar error when adding files from another project  like  paiego explained   My error was that I didn t check  Add to targets    As explained above  I deleted the references and added the files again but this time checking  Add to targets

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once i got   18 duplicate symbols for architecture i386 clang  error  linker command failed with exit code 1   For me this was due to that i have used  const NSInteger  in my switch case    What i did is change the const NSInteger to enum  and replace the reference with enum values   This fixed the error for me

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That can happen if the same  m file is referenced multiple times in your target s  Compile Sources  section in  Build Phases   Remove duplicate entries and you should be fine

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It look like the class Algebra5FirstViewController is compile multiple time    Can you make sure that the  m and  mm is only included once in your project sources in Xcode  You can also confirm this by checking in the compile log  last icon at the right  next to the breakpoints icon  and see that confirm that it is only compiled once   Also  if this class is part of a library that you link against and you have a class with the same name  you could have the same error   Finally  you can try a clean and rebuild  just in case the old object files are still present and there is some junk in the compiled files  Just in case     EDIT  I also note that the second reference is made in the file for ExercisesViewController  Maybe there is something in this file  Either you  imported the Algebra5FirstViewController file instead of the  h  or the ExercisesViewController has  implementation  Algebra5FirstViewController  instead of  implementation  ExercisesViewController   or there was some junk with this file that will cleaned with a Clean an Rebuild

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This happens either  some files are missing in the  Compile Sources  section  or duplicate entries are found for some file s   In my case  I had duplicate entries for two files  I deleted one entry for each of the files  that solved my problem  Hope this helps

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I got this issue because I accidentally imported the  m instead of the  h   Hope reading this saves someone with same problem some time

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I had the same error  I had imported a audio frame work that i was no longer using  I removed it  DO NOT DELETE IT   and it built successfully

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In one case  I saw this error when dragging a new class   h and  m into the project  The only solution I found was to remove the references to these files and then add them back via the project menu

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I met it when import a ViewController m in TableViewController  Try to delete   import  ViewController m   if it exited  Hope this help

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I had same problem  Got it solved   If you have imported any files into project then check  m  main  file for same does exists in Targets  Project Name  -  Build Phases -  Compile Sources   If file does not exists then include it using     Add button shown  Also  if duplicate files exists  if any  then delete it   Now press cmd shift k to clean the project  New Build should not display this error

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Simply cleaning CMD   SHIFT   K  then building CMD   B worked for me

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This occurred for me when I named a UILabel reference and an int the same thing  I didn t get an error when I typed it only when I tried to run it so I didn t realize that that was the problem  but if you have something like a label which is the  score  and you call it score  and name an int which is the score also score then this problem occurs

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I m posting a new answer to this because I ran into this error and had to use a different solution that I think is specific to iOS 9    I had to explicitly disable the Enable Bitcode in Build Settings  which is automatically turned on in the update   Referenced answer  New warnings in iOS 9

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I had this same issue with a library  and I tried all of the answers listed here and nothing helped   I ended up simply removing the library from Link Binary With Libraries and then re-adding it and it worked fine

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Link Binary With Libraries  had old project name pod library  Fixed after removal    List item Project Build Phases Link Binary With Libraries Remove deprecated library

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also had this problem by declaring a const   NSString in the header file  incorrectly  instead of the implementation file  correctly

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The only  and unfailing  way to resolve this issue is building test from command line   xcodebuild -workspace MyProject xcworkspace  -scheme MyScheme -sdk iphonesimulator -destination  platform iOS Simulator name iPhone 7 OS 10 3 1  test   So  at this point  your compilation will surely fail but you ll see all linking problem  In my case  I had several problem such as    ld  framework  Foo  not found To resolve this  you need to on your target  BuildSettings- Linking- OtherLinkerFlags and remove  Foo  framework    Use of unresolved identifier  ClassName    To resolve this  I need to add check file s target membership to UITest target too    Other possible problems will be raised by xcodebuild and you can easily fix it

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I found this article that provided a solution for me  It pertains to Xcode 7 where the default for No Common Blocks is Yes rather than No in previous versions    This is a quote from the article      The problem seems to be that the  No common blocks  in the  Apple LLVM   6 1 - Code Generation  section in the Build settings pane is set to Yes  in the latest version of Xcode    This caused what I will describe as circular references where a class that was included in my Compile Sources was referenced via a  import in another source file  appDelegate m   This caused duplicate blocks for variables that were declared in the original base class   Changing the value to No immediately enabled my app to compile and resolved my problem

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In my case I had a reference to a library in Other Linker Flags  Removing it got rid of the error

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Running Xcode 4 6 3 on OSX 10 7 5 was able to fix this error by changing Architectures to Native Architecture of Build Machine from   NATIVE ARCH ACTUAL

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I received this once by  accidentally  importing both the  h and  m files into the same class

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It seems that for m  I dragged the files into the project and after that didn t work  clicked file  add files to project   Both were the incorrect approach  just drag it into the projects folder  in finder  that houses the other  h and  m files

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Variations on this issue can occur if you have a missing library or file  Check there aren t any missing files in your Project Explorer  they ll be written in red if Xcode can t find them

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XCODE 7 1 UPDATE   First Option That Worked    I changed the Deployment Target from 7 1 to 8 1 and the error went away    Hope that helps someone    UPDATE  day 2   Second time I m back here in 2 days    On day 2 I started to get more errors in addition to this annoying error  The problem was a conflicting file that Xcode didn t recognize  I used the links below as help     quot  OBJC CLASS   viewsampleViewController quot   referenced from     ld  warning  directory not found for option      And ultimately      quot  OBJC CLASS   viewsampleViewController quot   referenced from    I was deleting everything from the FrameWork Search Paths   Compile Resources   Run Script Phases   the pods and then re-installing them again to ultimately find success   The issue on my size  on day 2  was more of a problem with conflicting files or files that Xcode didn t recognize    But ultimately  removing everything  mentioned above and in the links   cleaning a lot of times and reinstalling the pods frameworks run script phases helped     Really hope this helps someone

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I got this error while implementing a subclass without the necessary framework added  MPMoviePlayerController without the MediaPlayer framework  in this example

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linker command failed with exit code 1  use -v to see invocation  - I got this error when running a phonegap application on iPhone  I changed Build Active Architecture Only to Yes and it worked fine

[objective-c] build failed with: ld: duplicate symbol _OBJC_CLASS_$_Algebra5FirstViewController

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