ios GCD 用法

1、GCD线程

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{       // 耗时的操作       dispatch_async(dispatch_get_main_queue(), ^{           // 更新界面       });   });

2、GCD延时

dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(sec * 0.03 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{    //延时后的操作});