多线程CGD调度组原理

我们常用的GCD调度组方式

 //GCD常用调度组写法
 -(void)demo1{

     //创建调度组和队列
     dispatch_group_t group = dispatch_group_create();
     dispatch_queue_t queue = dispatch_queue_create("ChangYong", DISPATCH_QUEUE_CONCURRENT);

     //将任务添加到调度组
     dispatch_group_async(group, queue, ^{
         NSLog(@"耗时操作_11111111");
     });
     dispatch_group_async(group, queue, ^{
         //模拟耗时操作
         [NSThread sleepForTimeInterval:];
         NSLog(@"耗时操作_22222222");
     });
     dispatch_group_async(group, queue, ^{
         NSLog(@"耗时操作_33333333");
     });

     //所有任务执行完毕后执行的任务
     dispatch_group_notify(group, dispatch_get_main_queue(), ^{
         NSLog(@"所有任务执行完毕, 更新UI操作");
     });
 }

GCD调度组原理

 //GCD调度组原理方法
 -(void)demo2{

     //创建调度组和队列
     dispatch_group_t group = dispatch_group_create();
     dispatch_queue_t queue = dispatch_queue_create("YuanLi", DISPATCH_QUEUE_CONCURRENT);

     //任务1
     dispatch_group_enter(group);
     dispatch_async(queue, ^{
         NSLog(@"任务1");
         dispatch_group_leave(group);
     });

     //任务2
     dispatch_group_enter(group);
     dispatch_async(queue, ^{
         [NSThread sleepForTimeInterval:];
         NSLog(@"任务2");
         dispatch_group_leave(group);
     });

     //任务3
     dispatch_group_enter(group);
     dispatch_async(queue, ^{
         NSLog(@"任务3");
         dispatch_group_leave(group);
     });

     //任务全部执行完毕
     dispatch_group_notify(group, dispatch_get_main_queue(), ^{

         NSLog(@"任务执行完毕, 刷新UI");
     });

     //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
     //dispatch_group_wait(group, DISPATCH_TIME_FOREVER);

     NSLog(@"Hello");
 }