ios - NSURLRequest 缓存策略

Question

我正在使用 NSURLRequest 和 CachePolicy 在 NSData 中下载一个 plist。当我更改我的 plist 的内容时，我的应用程序忽略了这一点并仍然显示缓存的内容。缓存持续多久？如果是这样，是否有一个选项可以说明缓存数据会持续多长时间？如果服务器上的数据比缓存更新从服务器加载数据或者它是否等于缓存使用缓存，有没有办法检查 NSURLRequest？

Answer 1

查看 URLLoadingSystem docs 中的控制响应缓存.

您可以在委托(delegate)方法中添加自己的日期

-(NSCachedURLResponse *)connection:(NSURLConnection *)connection
                 willCacheResponse:(NSCachedURLResponse *)cachedResponse

使用缓存系统要容易得多 ASIHTTPRequest .我推荐使用这个 URL 加载系统。

来自苹果文档:

The example in Listing 6 prevents the caching of https responses. It also adds the current date to the user info dictionary for responses that are cached.

-(NSCachedURLResponse *)connection:(NSURLConnection *)connection
                 willCacheResponse:(NSCachedURLResponse *)cachedResponse
{
    NSCachedURLResponse *newCachedResponse = cachedResponse;

    if ([[[[cachedResponse response] URL] scheme] isEqual:@"https"]) {
        newCachedResponse = nil;
    } else {
        NSDictionary *newUserInfo;
        newUserInfo = [NSDictionary dictionaryWithObject:[NSCalendarDate date]
                                                 forKey:@"Cached Date"];
        newCachedResponse = [[[NSCachedURLResponse alloc]
                                initWithResponse:[cachedResponse response]
                                    data:[cachedResponse data]
                                    userInfo:newUserInfo
                                    storagePolicy:[cachedResponse storagePolicy]]
                            autorelease];
    }
    return newCachedResponse;
}