// .h文件
@interface SingleTon : NSObject
/** 获取单例对象*/
+ (instancetype)sharedInstance;
+ (instancetype)new __attribute__((unavailable("new unavailable, call sharedInstance instead")));
- (instancetype)init __attribute__((unavailable("init unavailable, call sharedInstance instead")));
+ (instancetype)alloc __attribute__((unavailable("alloc unavailable, call sharedInstance instead")));
@end// .m文件
static SingleTon *_instance;
@implementation SingleTon
+ (instancetype)sharedInstance {static dispatch_once_t onceToken;dispatch_once(&onceToken, ^{_instance = [[super alloc] initInstance];});return _instance;
}- (instancetype)initInstance {return [super init];
}+ (instancetype)allocWithZone:(struct _NSZone *)zone {static dispatch_once_t onceToken;dispatch_once(&onceToken, ^{_instance = [super allocWithZone:zone];});return _instance;
}- (id)copyWithZone:(NSZone *)zone {return _instance;
}
@end

- (instancetype)init __attribute__((unavailable("init unavailable, call sharedInstance instead")));

- (instancetype)init NS_UNAVAILABLE;

- (instancetype)init {[super doesNotRecognizeSelector:_cmd];return nil;
}

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[TestManager init]: unrecognized selector sent to instance 0x600000001150'

// NSAssert断言
- (instancetype)init {NSAssert(false,@"init unavailable, use sharedInstance instead");return nil;
}// NSException
- (instancetype)init {[NSException raise:NSGenericExceptionformat:@"init unavailable. use +[%@ %@] instead",NSStringFromClass([self class]),NSStringFromSelector(@selector(sharedInstance))];return nil;
}