I’m seeing this error on an iOS 4.3.5 handset where my app has been installed via an ad hoc deployment (downloaded over HTTP):
Dyld Error Message:
Symbol not found: _OBJC_CLASS_$_NSJSONSerialization
Expected in: /System/Library/Frameworks/Foundation.framework/Foundation
My code in the app doesn’t call iOS 5 libraries unless a class has been shown to exist (i.e. if(NSClassFromString(@"NSJSONSerialization")!=nil) so the issue isn’t that calls are being made to iOS 5 libraries on an iOS 4 device.
The app itself contains a static library which is my own code, and is where the NSJSONSerialization references exist.
The app works perfectly on the iOS 4.3 device if run directly from xcode (i.e. the iPhone attached to the development machine via USB cable). However, when run on the same device via the adhoc deployment, I see the crash.
The adhoc archive is built via Product->Archive in xcode 4, and then I use the ‘Distribute’ button to create the Ad-Hoc deployment .ipa file.
The app crashes almost instantly, leaving me to think that perhaps none of my code is being called at all, and that it’s my Archive build settings that may be incorrect here?
Many thanks in advance for any time spent helping!
This sounds like the exact same issue I ran into in this answer. There’s something slightly different about the way that weak linking is being handled when dealing with static libraries on building and archiving vs. direct installation via Xcode. The latter seems to handle class- and function-level weak linking as it should (since Xcode 4.3). However, when archiving a project containing a static library, that weak linking is not being used correctly.
In my case, I needed to manually weak link the problematic iOS framework in the application using my static library in order for it to work when building for ad hoc or App Store distribution. To do this, go to your project’s build settings, go to the Build Phases tab, and expand the Link Binary With Libraries grouping. Find the offending framework (in my case it was CoreVideo.framework, but it sounds like you may need to do this for Foundation.framework) and change it from Required to Optional.
This should clear up your weak-linking issue. I’m investigating this further to see if there’s a build setting I’m missing or if this is a linker bug.