gistfile1.txt

#import <objc/runtime.h>
#import <objc/message.h>
__attribute__((constructor)) static void PSPDFFixCollectionViewUpdateItemWhenKeyboardIsDisplayed(void) {
    @autoreleasepool {
    if ([UICollectionViewUpdateItem class] == nil) return; // pre-iOS6.
    if (![UICollectionViewUpdateItem instancesRespondToSelector:@selector(action)]) {
            IMP updateIMP = imp_implementationWithBlock(^(id _self) {});
            Method method = class_getInstanceMethod([UICollectionViewUpdateItem class], @selector(action));
            const char *encoding = method_getTypeEncoding(method);
            if (!class_addMethod([UICollectionViewUpdateItem class], @selector(action), updateIMP, encoding)) {
                PSPDFLogError(@"Failed to add action: workaround");
            }
        }
    }
}