为什么我们在这里使用 ephemeralSessionConfiguration？

Question

- (void)application:(UIApplication *)application performFetchWithCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler
{
    if (self.photoDatabaseContext) {
        NSURLSessionConfiguration *sessionConfig = [NSURLSessionConfiguration ephemeralSessionConfiguration];
        sessionConfig.allowsCellularAccess = NO;
        sessionConfig.timeoutIntervalForRequest = BACKGROUND_FLICKR_FETCH_TIMEOUT;
        NSURLSession *session = [NSURLSession sessionWithConfiguration:sessionConfig];
        NSURLRequest *request = [[NSURLRequest alloc] initWithURL:[FlickrFetcher URLforRecentGeoreferencedPhotos]];
        NSURLSessionDownloadTask *task = [session downloadTaskWithRequest:request
                                                        completionHandler:^(NSURL *localFile, NSURLResponse *response, NSError *error) {
                                                            if (error) {
                                                                NSLog(@"Flickr background fetch failed: %@", error.localizedDescription);
                                                                completionHandler(UIBackgroundFetchResultNoData);
                                                            } else {
                                                                [self loadFlickrPhotosFromLocalURL:localFile
                                                                                       intoContext:self.photoDatabaseContext
                                                                               andThenExecuteBlock:^{
                                                                                   completionHandler(UIBackgroundFetchResultNewData);
                                                                               }
                                                                 ];
                                                            }
                                                        }];
        [task resume];
    } else {
        completionHandler(UIBackgroundFetchResultNoData);
    }
}

似乎合乎逻辑的是必须有 backgroundSessionConfigurationWithIdentifier 而不是 ephemeralSessionConfiguration 因为它正在后台加载。但是斯坦福 iOS 课程的 Paul Hegarty 说第二个更好。为什么？他说了一些离散抓取的东西，我没听懂

Answer 1

ephemeralSessionConfiguration：与默认配置类似，只是所有session-related数据都存储在内存中。将其视为“私有”session。 backgroundSessionConfiguration：让session在后台执行上传或下载任务。即使应用程序本身被暂停或终止，传输也会继续。更多信息：https://www.raywenderlich.com/110458/nsurlsession-tutorial-getting-started

为什么我们在这里使用 ephemeralSessionConfiguration？

Why we are using ephemeralSessionConfiguration here?

ios

nsurlsession