iOS 中 GCD 的使用

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

});

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

});

串行 DISPATCH_QUEUE_SERIAL

并行 DISPATCH_QUEUE_SERIAL_INACTIVE

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);

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

});

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

 NSLog(@"%zu", s);

});

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);