NSFilemanager 上传新文件，但 UIWebView 显示缓存版本 [英] NSFilemanager uploads new file, but UIWebView shows cached version

问题描述

我正在构建的应用程序需要定期检查更新文件的已知位置.它恰好是一个PDF.如果经过 x 时间，应用程序需要上传文件的新副本.以下代码片段有效.它下载文件.但该应用程序会显示 PDF 的缓存版本，而不是新版本.我通过查看应用程序包确认了这一点.这段代码运行后，Documents目录下肯定有一个新文件.但是在捆绑包的 tmp/DiskImageCache-[随机乱码字符串] 中有一份旧版 PDF 的副本 - 这就是我的 UIWebView 显示的内容.

An app I'm building needs to periodically check a known location for an updated file. It happens to be a PDF. If x amount of time has passed, the app needs to upload a new copy of the file. The following code snippet works. It downloads the file. But the app displays a cached version of the PDF instead of the new one. I confirmed this by looking in the app bundle. After this code runs, there is definitely a new file in the Documents directory. But in the bundle's tmp/DiskImageCache-[random gibberish string] there is a copy of the old version of the PDF - and that is what is being displayed by my UIWebView.

我搜索了 NSFileManager 文档，当然，也遇到了麻烦，但我一直无法找到让应用程序显示新上传而不是缓存版本的 PDF 的方法.

I searched the NSFileManager docs and of course, schmoogled up a storm, but I have not been able to find a way to get the app to show the new upload instead of the cached version of the PDF.

非常感谢您对这个问题提供的任何帮助.

Thanks a ton for any assistance you can render with this problem.

   -(void) checkFile:(NSString *)url andSaveTo:(NSString __autoreleasing *)filename {

    NSFileManager *manager = [NSFileManager defaultManager];
    NSError *error = nil;      
    NSDictionary *attributes = nil;

    if ([manager fileExistsAtPath:filename]) {

       attributes = [manager attributesOfItemAtPath:filename error:nil];

        double updateInterval = [[attributes fileCreationDate] timeIntervalSinceNow];
        cacheInterval = CacheInterval;

        if (ABS(updateInterval) > CacheInterval) {
         [self downloadFile:url andSaveTo:fileName];
        }
    }
}

推荐答案

你总是可以通过在你的 url 中附加一个随机数作为参数来阻止缓存

you can always thwart caching by appending a random number to your url as a parameter

例如:地址/yourfilehere.pdf?rand=0323094230948203984并每次给你的长随机参数一个新的随机生成的数字

ex: address/yourfilehere.pdf?rand=0323094230948203984 and give your long random parameter a new randomly generated number each time

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