dispatch_source_create不适用于部署目标iOS 6

Question

下面的代码适用于部署目标设置为iOS 6以下但是如果我更改为6.0则返回＆＃34; OS_dispatch_source＆＃34;而不是＆＃34; dispatch_source_t＆＃34;。因此，只要尝试使用＆＃34; timeoutTimer＆＃34;它就会崩溃。请帮忙。

    dispatch_source_t timeoutTimer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0,
                                                         dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0));

dispatch_source_t timeoutTimer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0));