Re: [Boost-users] [boost::function] Getting base class pointer of functor ?

From: Johannes Stallkamp (jstallkamp_at_[hidden])
Date: 2008-04-03 18:12:56

Steven Watanabe schrieb:
[...]
>
> Long answer:
>
> Boost.Function stores a pointer, but it's a void pointer so it loses all
> type information.  The type information is stored separately, using
> std::type_info.  With this setup, there is no way to determine
> whether the type that you ask for is a base of the stored type.
> The only way to implement this is to create a class the inherits
> multiply from the stored type and a common base.  This allows
> the use of dynamic_cast to cross cast.  This unfortunately requires
> that it be possible to derive from the stored type, so built-ins become
> a special case.  In addition, it makes the small buffer optimization
> difficult to implement seriously hurting performance even when this
> feature is not used.
Alright, I see. Thanks for your detailed explanation. I modified the
approach so that I don't have to store (and therefore copy) the pointer
to the boost::any any more. Probably not optimal either, but I have to
see. For now, it works.

Thanks
Johannes