dispatch_barrier_async、dispatch_apply、dispatch_block_notify、dispatch_group_notify

• 2、dispatch_apply
• dispatch_apply类似一个for循环&＃xff0c;会在指定的dispatch queue中运行block任务n次&＃xff0c;如果队列是并发队列&＃xff0c;则会并发执行block任务&＃xff0c;dispatch_apply是一个同步调用&＃xff0c;block任务执行n次后才返回。
  简单的使用方法&＃xff1a;

dispatch_queue_t queue &＃61; dispatch_queue_create("myqueue", DISPATCH_QUEUE_CONCURRENT);
//并发的运行一个block任务5次
dispatch_apply(5, queue, ^(size_t i) {NSLog(&＃64;"do a job %zu times",i&＃43;1);
});
NSLog(&＃64;"go on");


输出结果&＃xff1a;

GCDTests[10029:760640] do a job 2 times
GCDTests[10029:760640] do a job 1 times
GCDTests[10029:760640] do a job 3 times
GCDTests[10029:760640] do a job 5 times
GCDTests[10029:760640] do a job 4 times
GCDTests[10029:760640] go on

• 3、dispatch_block_notify
• dispatch_block_notify当观察的某个block执行结束之后立刻通知提交另一特定的block到指定的queue中执行&＃xff0c;该函数有三个参数&＃xff0c;第一参数是需要观察的block&＃xff0c;第二个参数是被通知block提交执行的queue&＃xff0c;第三参数是当需要被通知执行的block&＃xff0c;函数的原型:

void dispatch_block_notify(dispatch_block_t block, dispatch_queue_t queue,dispatch_block_t notification_block);


具体使用的方法:

dispatch_queue_t queue &＃61; dispatch_queue_create("queue", DISPATCH_QUEUE_SERIAL);dispatch_block_t previousBlock &＃61; dispatch_block_create(0, ^{NSLog(&＃64;"previousBlock begin");[NSThread sleepForTimeInterval:1];NSLog(&＃64;"previousBlock done");});dispatch_async(queue, previousBlock);dispatch_block_t notifyBlock &＃61; dispatch_block_create(0, ^{NSLog(&＃64;"notifyBlock");});//当previousBlock执行完毕后&＃xff0c;提交notifyBlock到global queue中执行dispatch_block_notify(previousBlock, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), notifyBlock);


运行结果&＃xff1a;

GCDTests[17129:895673] previousBlock begin
GCDTests[17129:895673] previousBlock done
GCDTests[17129:895673] notifyBlock