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我正在尝试通过记录 NSURLCache 周围的内存统计信息来确认 URL 缓存。

我已经扩展了基础 NSURLCache 如下：

@implementation  MarksCache : NSURLCache

- (NSCachedURLResponse *) cachedResponseForRequest:(NSURLRequest *)request;
{
    NSString *myString = [request.URL absoluteString];
    DDLogVerbose(@"URL CACHE GET : PRE  : %@ %d %d %d %d", myString,
                 [NSURLCache sharedURLCache].currentDiskUsage ,
                 [NSURLCache sharedURLCache].currentMemoryUsage,
                 [NSURLCache sharedURLCache].diskCapacity,
                 [NSURLCache sharedURLCache].memoryCapacity);

    NSCachedURLResponse *resp = [super cachedResponseForRequest:request];
    //NSURLResponse *rp = [resp response];
    //NSString *rpdesc = [rp description];

    //NSData *data = [resp data];
    //NSString *respdesc = [resp description];
    //NSString *selfdesc = [super description];

    DDLogVerbose(@"URL CACHE GET : POST : %@ %d %d %d %d", myString,
                 [NSURLCache sharedURLCache].currentDiskUsage ,
                 [NSURLCache sharedURLCache].currentMemoryUsage,
                 [NSURLCache sharedURLCache].diskCapacity,
                 [NSURLCache sharedURLCache].memoryCapacity);

    return resp;
}

- (void)storeCachedResponse:(NSCachedURLResponse *)cachedResponse forRequest:(NSURLRequest *)request
{
    NSString *myString = [request.URL absoluteString];
    DDLogVerbose(@"URL CACHE SET : PRE  : %@ %d %d %d %d", myString,
                 [NSURLCache sharedURLCache].currentDiskUsage ,
                 [NSURLCache sharedURLCache].currentMemoryUsage,
                 [NSURLCache sharedURLCache].diskCapacity,
                 [NSURLCache sharedURLCache].memoryCapacity);
    [super cachedResponseForRequest:request];
    DDLogVerbose(@"URL CACHE SET : POST : %d %d %d %d",
                [NSURLCache sharedURLCache].currentDiskUsage ,
                [NSURLCache sharedURLCache].currentMemoryUsage,
                [NSURLCache sharedURLCache].diskCapacity,
                [NSURLCache sharedURLCache].memoryCapacity);
}

@end

我还有执行以下操作的按钮代码：

- (IBAction)onClearButtonPress:(id) sender{
    DDLogVerbose(@"TestViewController onClearButtonPress : START : PRE : %d %d %d %d", 
    [NSURLCache sharedURLCache].currentDiskUsage , 
    [NSURLCache sharedURLCache].currentMemoryUsage, 
    [NSURLCache sharedURLCache].diskCapacity,  
    [NSURLCache sharedURLCache].memoryCapacity);

    [NSURLCache sharedURLCache].removeAllCachedResponses;

    DDLogVerbose(@"TestViewController onClearButtonPress : START : POST : %d %d %d %d", 
    [NSURLCache sharedURLCache].currentDiskUsage , 
    [NSURLCache sharedURLCache].currentMemoryUsage, 
    [NSURLCache sharedURLCache].diskCapacity,  
    [NSURLCache sharedURLCache].memoryCapacity);

    }

当我单击视图上的一些测试按钮以触发 URLConnection 事件时，我看到使用正确的 URL 调用这些方法。但是，缓存内存和磁盘使用统计信息永远不会改变。

来自日志的示例

URL CACHE SET : PRE  : https://<domain.com>/resources/images/bg/bg-blue.png 1970176 0 10000000 512000
URL CACHE SET : POST : https://<domain.com>/resources/images/bg/bg-blue.png 1970176 0 10000000 512000

URL CACHE GET : PRE  : https://<domain.com>/resources/images/bg/bg-footer.png 1970176 0 10000000 512000
URL CACHE GET : POST : https://<domain.com>/resources/images/bg/bg-footer.png 1970176 0 10000000 512000

TestViewController onClearButtonPress : START : PRE : 1970176 0 10000000 512000
TestViewController onClearButtonPress : EXIT : POST : 1970176 0 10000000 512000

URL CACHE SET : PRE  : https://<domain.com>/resources/images/bg/bg-footer.png 1970176 0 10000000 512000
URL CACHE SET : POST : https://<domain.com>/resources/images/bg/bg-footer.png 1970176 0 10000000 512000

这让我相信：

1 - 我做错了什么，没有正确观察缓存行为

2 - 这个缓存并不是真正的缓存

任何想法将不胜感激。

4

1 回答 1

1

我不久前想通了这一点，并想发布答案。我已将我的代码作为代表： NSURLConnection - connection:willCacheResponse

该方法允许您在缓存行为发生之前覆盖它。我只是简单地登录它以查看我的响应是可缓存的，而忘记实际进行任何缓存。修复后，我的内存统计记录确实显示项目进入和退出缓存。

URL 加载系统编程指南

于 2012-12-13T13:44:00.633 回答