From: "Jeremy Maitin-Shepard" <jeremy@jeremyms.com> ...
Say, a Train class is complex as it has a *lot* of stuff. We serialize/unserialize the class to/from XML using 'convert'. Train has op>>() op<<().
I don't like default_value as a customization point either. However, it seems that for a non-default constructable type, operator>> is likely not the ideal interface for unserialization.
Agreed. And you nailed it -- for unserialization we've been in fact moving towards more direct approach. As simple as a class needs to provide a specific constructor "class::class(xml::element const&)" for that purpose. I personally like it better. Less overhead; do what you mean; easier to follow. As with long-running projects is does not happen overnight especially when the old supporting framework is in place.
How would you use your unserialization functionality separately from the convert library? Presumably you would need some way to obtain a constructed instance in a form suitable for invoking operator>>. If the non-default-constructable type has any members that aren't default constructable, you would have to somehow construct the members as well.
I am not sure I understand. A non-default-constructable object is constructed in whatever way it can be constructed and then is fed to convert::from(). Like // Constructed by whatever means available. Not the def. cntr direction fallback (direction::up); convert<direction>::result res = convert<direction>::from(str, fallback); direction reconstructed_from_str = res.value(); For big classes with value-semantics it might be quite an overhead. However, our classes are overwhelmingly pointer-semantics pimpl-based classes. That way we essentially apply something that probably can be called in-place re-initialization. For me it's somewhat over-engineered and we've been moving towards "class::class(xml::element const&)" for unserialization. Still, all the current features of 'convert' are needed. They will be (hopefully) used on smaller scale though. Not sure if answered your question to your satisfaction though. :-) V.