What NSKeyedArchiver probably does is have a dictionary that maps the original
object pointer values to the copied objects. So instead of just straight-out
copying an object, it does:
NSString* theKey = [NSString stringWithFormat: @"%p", theOriginal];
id theCopy = [objectCopies objectForKey: theKey];
if( !theCopy )
{
theCopy = [theOriginal copy];
[objectCopies setObject: theCopy forKey: theKey];
}
That way, every object only gets copied once, and the copy re-used in other
spots. That may be part of why it is slower. (NB - you could probably use an
NSValue +valueWithUnretainedPointer: or whatever as the key, I just quickly
typed this untested code into the e-mail)
Cheers,
-- Uli Kusterer
"The Witnesses of TeachText are everywhere..."
http://www.zathras.de
On Feb 14, 2013, at 3:57 AM, Ken Thomases <k...@codeweavers.com> wrote:
> Your question prompted me to try to design an analog of NSKeyedArchiver,
> NSCode, and NSCoding that would generate the new object graph on the fly as
> it went instead of producing a data object. The idea is that the copier (the
> analog of the archiver/coder) would know which objects had already been
> copied and so would avoid over-duplicating them in the new graph. However,
> that ends up being hard because each object has to copy its related object
> before it's complete enough to be registered with the copier. So, it isn't
> successful in avoiding the potential for infinite recursion.
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