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Re: Copying an object
- Subject: Re: Copying an object
- From: "Mark Hadfield" <m.hadfield(at)niwa.cri.nz>
- Date: Wed, 1 Sep 1999 12:04:38 +1200
- Newsgroups: comp.lang.idl-pvwave
- Organization: NIWA
- References: <37CB9D07.A381E318@gsiukltd.freeserve.co.uk> <MPG.firstname.lastname@example.org> <37CC0428.email@example.com> <MPG.firstname.lastname@example.org>
- Xref: news.doit.wisc.edu comp.lang.idl-pvwave:16405
David Fanning <email@example.com> wrote in message
> ...insurmountable problems. Randy Frank,
> who wrote much of this object code when he was at RSI,
> has sent me a private e-mail outlining even more problems
> than I was aware of on my own. For example, he points
> out that many times the model objects (which is what
> we were discussing earlier this morning) have parents.
> What should be done about those? Should the copy have
> the *same* parents, or any parents?
Remove the model object from its parent, copy it, and add it again
afterwards. Or am I missing something?
Entirely general solutions are very hard to come by in the object-oriented
world but if we know that an object is, say, an IDLgrModel, then we know it
has one parent (at most), we can get a reference to the parent from the
child's PARENT property, and we know the parent has Add and Remove methods.
Of course if I wanted to be perverse I could write an object that inherits
from IDLgrModel (so returns true for OBJ_ISA(...,'IDLgrModel')) but doesn't
obey these rules. But I don't want to be perverse.
> You can also try SAVEing and RESTOREing your objects,
> but this has the problem that sometimes the methods of
> restored objects can't be found. (See JD Smith's comments
> on this on my web page.)
That can certainly be a problem if you RESTORE an object that was SAVEd in a
previous session, but surely it is not an issue in the present case, where
we want to make a copy of an object (or object tree) that was created in the
present session. The copy operation needn't change any of the object
definitions, method definitions or object-method bindings.
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