#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
}

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
    NSLog(@"start"
 
);

//    dispatch_after(dispatch_time_t when,
//                   dispatch_queue_t queue,
//                   dispatch_block_t block);
    /**
     dispatch_time
     1. when DISPATCH_TIME_NOW
     2. delta (int64_t)(2 * NSEC_PER_SEC)) 納秒
     */
    dispatch_time_t after = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2
 
 * NSEC_PER_SEC));

    /**
     when 什麼時候執行程式碼
     queue 在哪個佇列執行
     block 要執行的任務
     */
    // 如果是在主執行緒執行延時的程式碼，就用 dispatch_get_main_queue()
    // 如果想在子執行緒執行延時的程式碼，就可以用 dispatch_get_global_queue(0, 0)
    dispatch_after(after, dispatch_get_global_queue(0, 0), ^{
        // 延時執行的程式碼
        NSLog(@"hello %@"
 
,[NSThread currentThread]);
    });
    NSLog(@"end");
}

@end