Category Composition

@interface NSObject (category)

@property (nonatomic, copy, setter = setObjectInfo:) id objectInfo;

@end

#import <objc/runtime.h>
static char kObjectInfoDictionaryKey;

@implementation NSObject (category)

- (void)setObjectInfo:(id)objectInfo {
    objc_setAssociatedObject(self, &kObjectInfoDictionaryKey, objectInfo, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

- (id)objectInfo {
    return objc_getAssociatedObject(self, &kObjectInfoDictionaryKey);
}

@end