iOS 中 GCD 的使用

1. 同步
   dispatch_sync(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

   });

2. 异步
   dispatch_sync(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

   });

3. 串行 DISPATCH_QUEUE_SERIAL

4. 并行 DISPATCH_QUEUE_SERIAL_INACTIVE

5. 主队列 dispatch_get_main_queue
   全局队列 dispatch_get_global_queue
   创建队列 dispatch_queue_create("w", DISPATCH_QUEUE_SERIAL);

6. 延迟
   dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(3 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{

   });

7. 循环
   size_t size = 3;
   dispatch_apply(size, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^(size_t s) {

    NSLog(@"%zu", s);
   

   });

8. 组队列 dispatch_group_t
   self.queue = dispatch_queue_create("com.chenzhou.queue", DISPATCH_QUEUE_SERIAL);

   dispatch_group_t myGruop = dispatch_group_create();
   dispatch_group_async(myGruop, self.queue, ^{

    sleep(2);
   

   });

   dispatch_group_async(myGruop, self.queue, ^{

    sleep(2);
   

   });
   // 异步函数 等待组加载完毕
   dispatch_group_notify(myGruop, dispatch_get_main_queue(), ^{
   self.sender.titleLabel.text = @"完成";
   });
   // 同步
   dispatch_group_wait(myGruop, DISPATCH_TIME_FOREVER);

   // 暂停 暂停后面添加的队列，前面已经加入不进入暂停
   dispatch_suspend(self.queue);

   // 继续
   dispatch_resume(self.queue);