多线程CGD调度组原理

 1 //GCD常用调度组写法
 2 -(void)demo1{
 3     
 4     //创建调度组和队列
 5     dispatch_group_t group = dispatch_group_create();
 6     dispatch_queue_t queue = dispatch_queue_create("ChangYong", DISPATCH_QUEUE_CONCURRENT);
 7     
 8     //将任务添加到调度组
 9     dispatch_group_async(group, queue, ^{
10         NSLog(@"耗时操作_11111111");
11     });
12     dispatch_group_async(group, queue, ^{
13         //模拟耗时操作
14         [NSThread sleepForTimeInterval:2];
15         NSLog(@"耗时操作_22222222");
16     });
17     dispatch_group_async(group, queue, ^{
18         NSLog(@"耗时操作_33333333");
19     });
20     
21     //所有任务执行完毕后执行的任务
22     dispatch_group_notify(group, dispatch_get_main_queue(), ^{
23         NSLog(@"所有任务执行完毕, 更新UI操作");
24     });
25 }

 1 //GCD调度组原理方法
 2 -(void)demo2{
 3     
 4     //创建调度组和队列
 5     dispatch_group_t group = dispatch_group_create();
 6     dispatch_queue_t queue = dispatch_queue_create("YuanLi", DISPATCH_QUEUE_CONCURRENT);
 7     
 8     //任务1
 9     dispatch_group_enter(group);
10     dispatch_async(queue, ^{
11         NSLog(@"任务1");
12         dispatch_group_leave(group);
13     });
14     
15     //任务2
16     dispatch_group_enter(group);
17     dispatch_async(queue, ^{
18         [NSThread sleepForTimeInterval:2];
19         NSLog(@"任务2");
20         dispatch_group_leave(group);
21     });
22     
23     //任务3
24     dispatch_group_enter(group);
25     dispatch_async(queue, ^{
26         NSLog(@"任务3");
27         dispatch_group_leave(group);
28     });
29     
30     //任务全部执行完毕
31     dispatch_group_notify(group, dispatch_get_main_queue(), ^{
32        
33         NSLog(@"任务执行完毕, 刷新UI");
34     });
35     
36     //等待上面代码执行完毕后在执行下面的代码, 参数2:等待超时时间
37     //dispatch_group_wait(group, DISPATCH_TIME_FOREVER);
38     
39     NSLog(@"Hello");
40 }