System/Library/Frameworks/Foundation.framework

_NSObservingObservation.h

NSObject
>
NSObservation
>
_NSConcreteObservation

@class NSString;

@interface _NSObservingObservation : _NSConcreteObservation <NSObserver>

@property (readonly) unsigned long long hash;
@property (readonly) Class superclass;
@property (readonly, copy) NSString *description;
@property (readonly, copy) NSString *debugDescription;


@end