GCD的延时操作

-(void)touchesBegan:(NSSet*)touches withEvent:(UIEvent *)event{     

//调用time延迟调用的方法    [self time];}-(void)time{     

//after在...之后调度,在这里我们只需要填写时间(2.0 * NSEC_PER_SEC)及延迟2.0秒后需要进行的操作 NSLog   

 dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{       

 NSLog(@"%@",[NSThread currentThread]);   

 });       

 NSLog(@"%@",[NSThread currentThread]);}

打印效果如下

2016-07-03 15:41:27.789 GCD使用[4210:302966]{number = 1, name = main}

2016-07-03 15:41:29.984 GCD使用[4210:302966]{number = 1, name = main}