IOS网络请求之NSURLSession使用详解

 3.)文件下载

// 创建url
  NSString *urlStr =@"http://www.easck.com/blog/950883/201701/950883-20170105104233581-62069155.png";
  NSURL *Url = [NSURL URLWithString:urlStr];
  // 创建请求
  NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:Url];
  // 设置请求超时
  [request setTimeoutInterval:30.0];
  // 创建会话
  NSURLSession *session = [NSURLSession sharedSession];
  
  NSURLSessionDownloadTask *downLoadTask = [session downloadTaskWithRequest:request completionHandler:^(NSURL * _Nullable location, NSURLResponse * _Nullable response, NSError * _Nullable error) {
    if (!error) {
      NSLog(@"download sucess : %@", location);
      NSData *data=[NSData dataWithContentsOfURL:location];
      UIImage *image=[UIImage imageWithData:data];
      dispatch_async(dispatch_get_main_queue(), ^{
        // 刷新界面...
        UIImageView *imageView =[[UIImageView alloc]init];
        imageView.image=image;
        [self.view addSubview:imageView];
        [imageView mas_makeConstraints:^(MASConstraintMaker *make) {
          make.center.equalTo(self.view);
          make.size.mas_equalTo(CGSizeMake(300, 300));
        }];
      });
    } else {
      NSLog(@"download error : %@", error.localizedDescription);
    }
  }];
  //启动任务
  [downLoadTask resume];