NSURLConnection data received after connectionDidFinishLoading

I have a question about NSURLConnection: I want download an image with:

NSURLConnection *theConnection=[[NSURLConnection alloc] initWithRequest:urlRequest delegate:self];

the first delegate called (correctly) is

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response

after this is called one time:

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data

and immediately:

- (void)connectionDidFinishLoading:(NSURLConnection *)connection

up to here everything is correct, but after connectionDidFinishLoading is fired once again the didReceiveData delegate for the same connection, I identify connection by:

NSString * connectionKey = [[[connection originalRequest] URL] absoluteString];

Is this possible?

update, more infos:

My app fire many simultaneous connections and I store infos for any connection in a dictionary, when a delegate was called I retrive connection info using the key: NSString * connectionKey = [[[connection originalRequest] URL] absoluteString]; for 99% of connections everything is all right but for one (avery time the same!) connection I have this behavior

---

here the complete implementation:

    - (void)downloadFileFromUrl:(NSURL *)url
                     inPath:(NSString *)completeFilePath
          dataReceivedBlock:(void (^)(long long byteDownloaded ,long long totalByte))dataReceivedBlock
                   endBlock:(void (^)(NSString * downloadPath, NSDictionary * responseHeaders))endBlock
                  failBlock:(void (^)(NSString * downloadPath, NSDictionary * responseHeaders, NSError * error))failBlock
{
    //save the connection infos       
NSMutableDictionary * requestData = [[NSMutableDictionary alloc] init];
if(dataReceivedBlock)
[requestData setObject:[dataReceivedBlock copy] forKey:@"dataReceivedBlock"];
if(endBlock)
[requestData setObject:[endBlock copy] forKey:@"endBlock"];
if(failBlock)
[requestData setObject:[failBlock copy] forKey:@"failBlock"];

        [requestData setObject:[NSNumber numberWithBool:YES] forKey:@"usingBlock"];
        [requestData setObject: completeFilePath forKey:@"downloadDestinationPath"];

    //delete the file if already on fs
    if([[NSFileManager defaultManager] fileExistsAtPath: completeFilePath])
        [[NSFileManager defaultManager] removeItemAtPath:completeFilePath error:nil];

    // Create the request.
    NSURLRequest * urlRequest = [NSURLRequest requestWithURL:url cachePolicy:NSURLCacheStorageAllowed timeoutInterval:TIME_OUT];
    NSURLConnection *theConnection=[[NSURLConnection alloc] initWithRequest:urlRequest delegate:self];
    if (!theConnection)
    {
        // Inform the user that the connection failed.
        failBlock(completeFilePath,nil,[NSError errorWithDomain:@"Connection fail" code:0 userInfo:nil]);
    }

    //add connection infos to the requests dictionary
    NSString * connectionKey = [[[theConnection originalRequest] URL] absoluteString];
    [self.requests setObject:requestData forKey:connectionKey];
}

here a delegate example:

- (void)connectionDidFinishLoading:(NSURLConnection *)connection

{

NSString * connectionKey = [[[connection originalRequest] URL] absoluteString];
NSMutableDictionary * requestData = [self.requests objectForKey:connectionKey];
NSFileHandle *file = [requestData objectForKey:@"fileHandle"];
[file closeFile];

//se la richiesta usa o no block
BOOL usingBlock = [[requestData objectForKey:@"usingBlock"] boolValue];
if(usingBlock)
{
    __block void (^endBlock)(NSString * , NSDictionary *) = [requestData objectForKey:@"endBlock"];
    if(endBlock)
        endBlock([requestData objectForKey:@"downloadDestinationPath"],[requestData objectForKey:@"responseHeaders"]);
}
else
    [self.delegate downloadEnded:[requestData objectForKey:@"responseHeaders"]];


//elimino dati richiesta
[self.requests removeObjectForKey:[NSString stringWithFormat:@"%@",connectionKey]];

//Inibisco standby
[UIApplication sharedApplication].idleTimerDisabled = NO;
}

Obviously the solution is really simple -_- The error is in the connection key identifier:

NSString * connectionKey = [[[connection originalRequest] URL] absoluteString];

my assumption is that key are unique, but if I make x parallel downloadS for the same file at the same url the assumption is wrong ;)