How to delay application quit?

FROM : Samvel
DATE : Mon Mar 24 02:55:17 2008

Hi,

I have defined class (say, Download) that uses NSURLConnection to 
download something from internet. My application is Cocoa with UI. I 
want to call:

[Download cancel]

and wait for notification from this class once user quits application. 
Reasoning: my Download class should cancel connection and perform some 
operations before object can be released in program. Thus I can not 
simply deallocate Download instance in dealloc method.

So, the idea is: instead of calling [myDownload cancel] from dealloc 
method delay application quit until all steps are completed in 
Download. Thus call [myDownload cancel] and wait for Notification say 
DownloadCanceled. Only then deallocate object.

Is there any way to figure out when user initiated quit application? 
How to delay it?

I think there should be something pretty much similar to awakeFromNib 
but called at the very end upon application quit.

Thanks.