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I have the following log output when running my application the iOS5 simulator. Both locations are the same. I get the following error for just about every class that is part of JSONKit.

Class JKSerializer is implemented in both /Users/myHomeDir/Library/Application Support/iPhone Simulator/5.0/Applications/33E6C55B-4883-48FF-BEFF-3FBA9C071CAB/MyApp.app/MyApp and /Users/myHomeDir/Library/Application Support/iPhone Simulator/5.0/Applications/33E6C55B-4883-48FF-BEFF-3FBA9C071CAB/MyApp.app/MyApp. One of the two will be used. Which one is undefined.

If this is appropriate, I have just ran a complicated merge, and I would prefer to not have to revert back to a previous version.

Any ideas on how this error occurs, how to prevent it, and how to fix it?

Mike D
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2 Answers2

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It's because the JSONKit.m implementation file is a member of more than one target and one of those targets has been included as a dependency on the other.

So, for example, checking target membership:

enter image description here

Here you can see that the file is a member of Pods-UnitTests and Pods.

This reflects the settings in Build Phases -> Compile Sources for each respective target.

Being a member of two targets isn't a problem per se. Rather the issue is that one of these targets is a dependency on the other. So Pods-UnitTests has a dependency on Pods. So, when you check the build transcript for unit tests, if you search for JSONKit.m, you'll find it twice. Once for libPods.a, and again for the Unit Tests target.

If you're not using CocoaPods then the solution is simply to remove the JSONKit.m file so it is only compiled once.

If you are using CocoaPods then I'm not sure what the solution is because although you don't want to compile the file twice, you will no doubt need to import the headers somewhere in your unit test code. As yet I'm not sure how to do that.

Here are some references:

https://github.com/CocoaPods/CocoaPods/issues/115

Class Foo is implemented in both MyApp and MyAppTestCase. One of the two will be used. Which one is undefined

http://sealedabstract.com/code/tired-of-getting-mach-o-linker-errors-when-unit-testing/

Community
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Max MacLeod
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  • Where did you find that Pods-UnitTests has a dependency to Pods? AFAICS libPods-UnitTests.a does not link to libPods.a Furthermore, if that was the case, you would get a Duplicate Symbol error instead. – qnoid Feb 11 '13 at 22:20
  • not sure if I can remember. Probably from doing a detailed look at the build transcript. I think this problem is caused by an as yet unresolved issue in Cocoapods. Not sure on the duplicate symbol. Something with the set up link vs runtime? – Max MacLeod Feb 12 '13 at 10:27
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Check to see if JSONKit is in a third party library that you are linking against.

There is a detailed post describing how to debug this very issue.

qnoid
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