iphone - NSURLCache 不缓存

Question

所以我对 NSURLCache 进行了子类化，每次我调用 loadHTMLFromString: 它都会调用 storeCachedRequest:forRequest: 然后是 cachedResponseForRequest:。这是我拥有的:

- (NSCachedURLResponse *)cachedResponseForRequest:(NSURLRequest *)request
{
    NSString *pathString = [[request URL] absoluteString];

    NSCachedURLResponse * response = [super cachedResponseForRequest:request];
    if (response != nil)
        return response;
    else {
        NSString* myString= @"testing";

        NSData* data=[myString dataUsingEncoding: NSASCIIStringEncoding ];

        //
        // Create the cacheable response
        //
        NSURLResponse *response =
        [[[NSURLResponse alloc]
          initWithURL:[request URL]
          MIMEType:[self mimeTypeForPath:pathString]
          expectedContentLength:[data length]
          textEncodingName:nil]
         autorelease];
        NSCachedURLResponse * cachedResponse =
        [[[NSCachedURLResponse alloc] initWithResponse:response data:data] autorelease];

        [self storeCachedResponse:cachedResponse forRequest:request] ;

        //NSLog(@"DEFAULT CACHE WITH URL %@", [[request URL] absoluteString]);
        return [super cachedResponseForRequest:request];
    }

    return nil;
}

- (void)storeCachedResponse:(NSCachedURLResponse *)cachedResponse forRequest:(NSURLRequest *)request
{
    [super storeCachedResponse:cachedResponse forRequest:request];

    NSLog(@"STORE CACHED RESPONSE WITH URL %@", [[request URL] absoluteString]);
}

问题是，当我在保存后立即调用 cachedResponseForRequest: 时，响应始终为零。这是为什么？

我有:

NSURLRequest * req = [NSURLRequest requestWithURL:[NSURL URLWithString:self.imageSource_]];
NSCachedURLResponse * response = [[NSURLCache sharedURLCache] cachedResponseForRequest:req];

if (response == nil)
    NSLog(@"RESPONSE IS NIL");
else {
    NSString* theString = [[NSString alloc] initWithData:response.data encoding:NSASCIIStringEncoding];
    NSLog(@"RESPONSE IS NOT NIL %@", theString);
}

它总是打印response is nil。 url字符串和之前一样存储缓存响应。由于某种原因，它不是缓存。我已将缓存大小设置为一定大小。

Answer 1

不是 100% 确定，但我认为您需要使用 NSURLConnection 返回的 NSURLResponse 而不是创建您自己的。我怀疑如果你只是创建一个 NSURLResponse 它没有为缓存设置任何 header ，所以 NSURLCache 假设它应该缓存这个特定的结果。