How to get content from URL asynchronously?

I'm trying here to create 开发者_开发知识库NSXMLParser from content of URL, it work perfectly well but is there way I can make URL content to be received asynchronously and later create NSXMLParser?

NSURL *url = [[NSURL alloc] initWithString: @"http://www.Xmlfile.com"];
NSXMLParser *parser = [[NSXMLParser alloc] initWithContentsOfURL:url];
[url release];

Use NSURLConnection to fetch the data asynchronously into an NSData, then use initWithData instead of initWithContentsOfURL.