I recently upgraded to Lion and Xcode 4.3.1 with the iOS 5 SDK, and the sharing library ShareKit is broken - it used method swizzling for its email handler. Apparently Apple has banned or at least attempted to phase out method swizzling.
ShareKit imports a file </usr/include/objc/objc-class.h>, which no longer exists, and defines its own method swizzling method SHKSwizzle. It uses this to alter MFMailComposeViewController's viewDidDisappear: method as follows:
SHKSwizzle([MFMailComposeViewController class], @selector(viewDidDisappear:), @selector(SHKviewDidDisappear:));
What do you think is the best and easiest way to work around this?
I have never experienced method swizzling related errors on even on newest XCode and iOS SDK. I use ShareKit 2.0. Though method swizzling is a thing to be avoided in my opinion.
The method swizzled is viewDidDisappear if I remember well. Look what it does. On iOS 5 you can achieve the same using completion block in - (void)dismissViewControllerAnimated:(BOOL)flag completion:(void (^)(void))completion.
Just change the way you dismiss the viewController in - (void)mailComposeController:(MFMailComposeViewController*)controller didFinishWithResult:(MFMailComposeResult)result error:(NSError*)error might be enough.
This is just an idea, how you might get rid of method swizzle.
The swizzling is only being used for email sharing. Use MFMailComposeViewController yourself, and strip the swizzling code out of ShareKit (it's in SHK.m).
来源：https://stackoverflow.com/questions/9900189/sharekit-method-swizzling-in-lion-xcode-4-3-1