在Apple'sdoc当我想捕获一个CoreFoundation对象时，我找不到我可以做什么。但在Apple的ConcurrencyProgrammingGuide.当调度对象不支持ARC时，示例代码似乎使用了一些代码，就像这样:voidaverage_async(int*data,size_tlen,dispatch_queue_tqueue,void(^block)(int)){//Retainthequeueprovidedbytheusertomake//sureitdoesnotdisappearbeforethecompletion//blockcanbecalled.di