dyld: Symbol not found: _OBJC_CLASS_$_NSNetService Error - ios

Question

So I have the following problem:
launching my application on iOS 8 on my iPhone 5s, I get no error, but launching my app on iOS 6.1.3 on my iPhone 3GS, I get this error:
dyld: Symbol not found: _OBJC_CLASS_$_NSNetService
Referenced from: /var/mobile/Applications/567E221A-FC5C-4011-90AD-E47E5FF033B1/BellyClient.app/BellyClient
Expected in: /System/Library/Frameworks/CFNetwork.framework/CFNetwork
in /var/mobile/Applications/567E221A-FC5C-4011-90AD-E47E5FF033B1/BellyClient.app/BellyClient
I imported a class named Server. The class uses the CFNetwork.framework, which contains the class NSNetService, which is avaiable since iOS 2.0.
Using NSClassFromString(#"NSNetService") is not really a solution I like.
I also don't know, why this error occurs, because the class NSNetService should be avaiable in iOS 6. Could it be the device?
I searched and found, that setting the framework to Optional, will solve this issue. But the problem is, that I cannot use the framework, when I run the application on iOS 6. When I do
if ([NSNetService class] == nil) {
NSLog(#"NSNetService is nil");
}
I get printed NSNetService is nil.
Is it possible to launch the app without crashing and without setting the framework as Optional
Thanks iComputerfreak

Answer 1

Try re-adding Foundation.framework:
Go to your project's target
Choose "General" tab
Under "Linked Frameworks an Libraries" look for Foundation.framework, select it and press the minus ('-') sign at the buttom to remove this framework.
Now press the plus sign ('+') and search for Foundation.framework - re-add it, and it's supposed to fix your crash.
Hope it works - it did for me.