(有码)OC单例

static Singleton* _instance =nil;

+ (Singleton *)shareSingleton{

    staticdispatch_once_t once;

    dispatch_once(&once, ^{

        _instance = [[superallocWithZone:nil]init];

    });

    return_instance;

}

+ (instancetype)alloc{

    return [selfshareSingleton];

}