NSDocument - preventing incomplete document from being saved

FROM : Lon Giese
DATE : Mon May 29 19:42:50 2006

What's the best way to prevent document closure when the document is in
an incomplete state?

I have tried overriding NSDocument's
canCloseDocumentWithDelegate:shouldCloseSelector:contextInfo:

but this is overly complicated because the main thrust of this method
is to let the user decide if he wants to save the document.

canCloseDocument

is very good, but it has been deprecated and is not called when
quitting the app (only widow closing) under 10.3.
How does the document architecture allow the programmer to decide if a
document should be closed? I just need a simple way to return NO if the
document is incomplete.