GCD线程延时

//swift中的线程延时

 let time: TimeInterval = 1.0
            DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + time) {
                print("延时1秒执行")
            }

//在主线程中延迟执行某动作，不会卡主主线程，不影响后面的东做执行

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

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

});

//在子线程中执行某动作，不会卡主整个线程

dispatch_queue_t queue= dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT,0);

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

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

});

//实现延迟，该线程本身在哪个线程中就再哪个线程中执行

NSURL *url = [NSURL URLWithString:@"http://59320.jpg.com"];

[selfperformSelector:@selector(download:) withObject:url afterDelay:3];

//利用sleep实现延迟(不要用这个，会卡住主线程，即后面的动作不会执行)

[NSThread sleepForTimeInterval:3];