[xsd-users] Default values for optional elements.

[Moss, David R (SELEX Comms) (UK Christchurch)]

Boris,

Yes, that sounds good - catching problems caused by changes at compile
time is definitely a good idea!

I did think there may be an issue with a scenario where the in-memory
value is set to that of the default (i.e. what should be serialised) but
that should just be treated as if it was any other non-default value I
guess.

Cheers,
Dave.

Dave Moss
SELEX Communications
Grange Road
Christchurch
Dorset  BH23 4JE
United Kingdom
Tel: + 44 (0) 1202 404841
Email: david.r.moss at selex-comm.com


-----Original Message-----
From: Boris Kolpackov [mailto:boris at codesynthesis.com]
Sent: 14 February 2006 08:10
To: Moss, David R (SELEX Comms) (UK Christchurch)
Cc: xsd-users at codesynthesis.com
Subject: Re: [xsd-users] Default values for optional elements.

Hi David,

Boris Kolpackov <boris at codesynthesis.com> writes:

> We will need to extend optional container with something like
set_default
> which will also require an extra flag to distinguish between the
normal
> value and default value cases (at the moment it's just an auto_ptr).
So
> things get a bit hairy and I would like to think some more about other
> options. Maybe we should use another container, optional_with_default?

I tend to think that creating a separate container (which inherits from
the optional container) with this additional logic is the best way to
go.
I also think it will make sense to use a different name for the accessor
function which has the additional, "default value" logic, something like
get_with_default. This way, when you have

return foo.bar ().get_with_default ();

and later change definition of bar not to have a default value or remove
the option that allow this behavior, you will get an error at compile-
time rather than at run-time. Any thoughts?


thanks,
-boris

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