- (IBAction)startDownloadingURL:(id)sender
{
    // create the request
    NSURLRequest *theRequest=[NSURLRequest requestWithURL:[NSURL URLWithString:@"http://www.apple.com/index.html"] cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:60.0];

    // create the connection with the request
    // and start loading the data
    NSURLDownload  *theDownload=[[NSURLDownload alloc] initWithRequest:theRequest delegate:self];

    if (!theDownload) {
        // inform the user that the download could not be made
    }
}

when i run the simulator , i got an error:

NSURLDownload undeclared ,first use in this fuction.

where can i import the library of NSURLDownload.