iOS当多个网络请求完成后执行下一步的方法详解

2020-01-21 02:45:01王冬梅

2017-12-04 18:04:27.699 DownImage[3584:306401] noRequest-0
2017-12-04 18:04:27.700 DownImage[3584:306405] noRequest-1
2017-12-04 18:04:27.701 DownImage[3584:306401] noRequest-2
2017-12-04 18:04:27.701 DownImage[3584:306405] noRequest-3
2017-12-04 18:04:27.702 DownImage[3584:306401] noRequest-4
2017-12-04 18:04:27.702 DownImage[3584:306405] noRequest-5
2017-12-04 18:04:27.703 DownImage[3584:306401] noRequest-6
2017-12-04 18:04:27.703 DownImage[3584:306401] noRequest-7
2017-12-04 18:04:27.704 DownImage[3584:306401] noRequest-8
2017-12-04 18:04:27.704 DownImage[3584:306401] noRequest-9
2017-12-04 18:04:27.772 DownImage[3584:306397] 2---2
2017-12-04 18:04:27.779 DownImage[3584:306401] 0---0
2017-12-04 18:04:27.782 DownImage[3584:306409] 1---1
2017-12-04 18:04:27.800 DownImage[3584:306405] 3---3
2017-12-04 18:04:27.851 DownImage[3584:306401] 6---6
2017-12-04 18:04:27.855 DownImage[3584:306397] 5---5
2017-12-04 18:04:27.915 DownImage[3584:306397] 7---7
2017-12-04 18:04:27.951 DownImage[3584:306397] 9---9
2017-12-04 18:04:27.953 DownImage[3584:306405] 8---8
2017-12-04 18:04:28.476 DownImage[3584:306409] 4---4

5.还是使用信号量semaphore完成4的需求


//5.semaphore---order
 UIButton *Btn5 = [UIButton buttonWithType:UIButtonTypeCustom];
 Btn5.frame = CGRectMake(100, 500, 100, 40);
 Btn5.backgroundColor = [UIColor grayColor];
 [Btn5 setTitle:@"order" forState:UIControlStateNormal];
 [Btn5 addTarget:self action:@selector(Btn5) forControlEvents:UIControlEventTouchUpInside];
 [self.view addSubview:Btn5];

//5.semaphore--order
-(void)Btn5{
 NSString *str = @"http://www.easck.com/p/6930f335adba";
 NSURL *url = [NSURL URLWithString:str];
 NSURLRequest *request = [NSURLRequest requestWithURL:url];
 NSURLSession *session = [NSURLSession sharedSession];
 dispatch_semaphore_t sem = dispatch_semaphore_create(0);
 for (int i=0; i<10; i++) {
  NSURLSessionDataTask *task = [session dataTaskWithRequest:request completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
   
   NSLog(@"%d---%d",i,i);
   dispatch_semaphore_signal(sem);
  }];
  [task resume];
  dispatch_semaphore_wait(sem, DISPATCH_TIME_FOREVER);
 }
 dispatch_async(dispatch_get_main_queue(), ^{
  NSLog(@"end");
 });
}

我们看看运行结果:


2017-12-05 10:17:28.175 DownImage[938:51296] 0---0
2017-12-05 10:17:28.331 DownImage[938:51289] 1---1
2017-12-05 10:17:28.506 DownImage[938:51289] 2---2
2017-12-05 10:17:28.563 DownImage[938:51289] 3---3
2017-12-05 10:17:28.662 DownImage[938:51289] 4---4
2017-12-05 10:17:28.733 DownImage[938:51296] 5---5
2017-12-05 10:17:28.792 DownImage[938:51296] 6---6
2017-12-05 10:17:28.856 DownImage[938:51286] 7---7
2017-12-05 10:17:29.574 DownImage[938:51289] 8---8
2017-12-05 10:17:29.652 DownImage[938:51286] 9---9
2017-12-05 10:17:29.653 DownImage[938:45252] end