NSURLRequest缓存无法正常工作

Question

我正在尝试缓存我的nsurlrequest数据.在此之前,我成功地从服务器下载数据,自从我尝试实现此缓存以来,它一直在使我的应用程序崩溃.我希望有人可以看看我到目前为止的代码,并帮助我让它工作..我想我已经完成了大约95%.

- (IBAction)setRequestString:(NSString *)string
{
    //Set database address
    NSMutableString *databaseURL = [[NSMutableString alloc] initWithString:@"http://127.0.0.1:29/"]; // imac development


    //PHP file name is being set from the parent view
    [databaseURL appendString:string];

    //call ASIHTTP delegates (Used to connect to database)
    NSURL *url = [NSURL URLWithString:databaseURL];

    //SynchronousRequest to grab the data, also setting up the cachePolicy
    NSURLRequest *request = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestReturnCacheDataElseLoad timeoutInterval:60.0]; //if request dose not finish happen within 60 second timeout.

    //This nsdata will be used to put the cache into
    NSData *cacheData = [[NSData alloc] init];
    //Create my own NSCachedURLResponse and add it to the cache
    NSURLResponse *responseToCache = [[NSURLResponse alloc] initWithURL:url MIMEType:@"text/xml" expectedContentLength:[cacheData length] textEncodingName:nil];
    //Set up the cache
    NSCachedURLResponse *cacheResponse = [[NSCachedURLResponse alloc] initWithResponse:responseToCache data:cacheData];
    [[NSURLCache sharedURLCache] storeCachedResponse:cacheResponse forRequest:request];

    //check if its really there
    NSLog(@"cache = %@", [[NSURLCache sharedURLCache] cachedResponseForRequest:request]);


    //If no cache do this stuff, connect to the db and perform these actions. I think this is what i am supposed to be doing.
    NSOperationQueue *queue = [[NSOperationQueue alloc] init];
    [NSURLConnection sendAsynchronousRequest:request queue:queue completionHandler:^(NSURLResponse *response, NSData *data, NSError *error)
    {
        if ([data length] > 0 && error == nil){
            [self receivedData:data];
        }else if ([data length] == 0 && error == nil){
            [self emptyReply];
        }else if (error != nil && error.code == NSURLErrorTimedOut){
            [self timedOut];
        }else if (error != nil){
            [self downloadError:error];
        }
    }];
}

Answer 1

感谢您的代码,我设法让它与您的示例一起工作.

cacheData是要缓存的数据,而不是缓存的位置.您必须自己获取并处理缓存.为了清楚起见,我举了一个例子:

NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:requestUrl cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:60.0];

NSCachedURLResponse *cachedURLResponse = [[NSURLCache sharedURLCache] cachedResponseForRequest:request];

NSData *responseData;

//check if has cache
if(cachedURLResponse && cachedURLResponse != (id)[NSNull null])
{
    responseData = [cachedURLResponse data];
}
else //if no cache get it from the server.
{
    __autoreleasing NSError *error = nil;
    NSHTTPURLResponse *response = nil;
    responseData = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];

    //..handle response and error

    //cache received data
    cachedURLResponse = [[NSCachedURLResponse alloc] initWithResponse:response data:responseData userInfo:nil storagePolicy:NSURLCacheStorageAllowed];
    //store in cache
    [[NSURLCache sharedURLCache] storeCachedResponse:cachedURLResponse forRequest:request];
}

//..handle responseData