在iOS中下载背景中的大量文件

Question

我有一个应用程序,我必须下载大量文件,从400到900文件,总共约1GB.

实现这一目标的最佳方法是哪种？

1. 其中一项NSURLSession任务入围了吗？
2. 一个NSURLSession并按包排队任务(例如10乘10)？
3. 多个NSURLSession不同的队列？

实际上我有一个NSURLSession所有任务(每个文件一个)排队,但有时我得到一个Lost connection to background transfer service.

这是我的代码:

if([[UIDevice currentDevice] isMultitaskingSupported])
{
    __block UIBackgroundTaskIdentifier bgTask;

    UIApplication *application = [UIApplication sharedApplication];

    bgTask = [application beginBackgroundTaskWithExpirationHandler:^{

        [application endBackgroundTask:bgTask];
        bgTask = UIBackgroundTaskInvalid;
    }];

    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

        NSString *uuidString;
        CFUUIDRef uuid = CFUUIDCreate(nil);
        uuidString = CFBridgingRelease(CFUUIDCreateString(nil, uuid));
        CFRelease(uuid);
        //            }

        NSURLSessionConfiguration *sessionConfiguration;

        if (SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(@"8.0"))
        {
            sessionConfiguration = [NSURLSessionConfiguration backgroundSessionConfigurationWithIdentifier:@"com.fiveflamesmobile.bakgroundDownload"];
        }
        else
        {
            sessionConfiguration = [NSURLSessionConfiguration backgroundSessionConfiguration:@"com.fiveflamesmobile.bakgroundDownload"];
        }
        sessionConfiguration.HTTPMaximumConnectionsPerHost = 5;
        sessionConfiguration.sessionSendsLaunchEvents = YES;
        sessionConfiguration.discretionary = YES;
        sessionConfiguration.timeoutIntervalForResource = 0; //NO timeout
        sessionConfiguration.timeoutIntervalForRequest = 0; //No timeout
        sessionConfiguration.networkServiceType = NSURLNetworkServiceTypeBackground;

        self.session = [NSURLSession sessionWithConfiguration:sessionConfiguration
                                                     delegate:self
                                                delegateQueue:nil];

        NSLog(@"##### ------- Sesion created succesfully");

        //    [self batchDownloading];

        for (id<FFDownloadFileProtocol> file in self.selectedCatalogProducto.downloadInfo.arrayFiles)
        {
            [self startDownloadFile:file];
        }

        NSLog(@"##### ------- Download tasks created successfully ------");

        [application endBackgroundTask:bgTask];
        bgTask = UIBackgroundTaskInvalid;
    });
}

}

Answer 1

一个 NSURLSession - 因为您只想处理一次基于会话的事情（例如身份验证）。

一个 NSOperationQueue - 同时运行多个操作。（参见属性操作计数）。第一次实现 NSOperation 可能有点棘手，但我确信这将是您最好的选择。 https://developer.apple.com/library/mac/documentation/Cocoa/Reference/NSOperationQueue_class/index.html

http://nshipster.com/nsoperation/

哦，顺便说一句，这是一种高度面向对象的方法，这总是很好 =)