[xsd-users] Customize sequence and optionals

[WEBER Stefan]

Hi Boris,
 
> > In my schema, the reason to make some elements optional is 
> mostly for 
> > convenience of the user writing the XML, such that the user 
> does not 
> > have to explicitly specify the element in case he wants to use the 
> > default value anyway. (e.g. for configuration data)
> 
> [...]
> 
> So am not sure how convenient elements with default values 
> will be in your situation.

Because the element defaults are not very useful in XML schema, I
implement this separately. I'm doing something like this:

template<class NonOptional, class Optional>
void createIfNotPresent(Optional& optionalType) {
    if(!optionalType) {
        optionalType.set( std::auto_ptr<NonOptional>(new
NonOptional()));
    }
}

The call to this is a bit ugly because I don't know how to derive the
NonOptional type from the Optional, e.g.:

MyOptionalType myOptional;
createIfNotPresent<MyNonOptionalType>(myOptional);

Isn't there a way to access the optionals containing type given the
optional one? Such that I could do something like:

template<class Optional>
void createIfNotPresent(Optional& optionalType) {
    if(!optionalType) {
        optionalType.set( std::auto_ptr<Optional::type>(new
Optional::type()));
    }
}

This would be much more convenient but I could not find a typedef in the
declaration of optional that seems to allow this.

Is there still a way to derive the non optional type from the optional
container?

Thanks,

Stefan

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