1#define NS_DESIGNATED_INITIALIZER __attribute__((objc_designated_initializer)) 2 3@class NSString; 4 5@interface B1 6-(instancetype)init; 7@end 8 9@interface S1 : B1 10@property (nonatomic) int prop; 11+(instancetype)s1; 12-(instancetype)initWithFoo:(NSString*)foo NS_DESIGNATED_INITIALIZER; 13@end 14