[xsd-users] polymorphism through xs:choice

[Boris Kolpackov]

Hi Harg,

Harg Tholan <hargtholan at gmail.com> writes:

> The question is, how can I retrieve the actual type of the referenced
> element? I need to know the actual type because I need to "dynamic cast"
> to it, but I can not know beforehand.

You cannot "retrieve" a C++ type at runtime and dynamic_cast to it. C++
is a compiled, statically-type language. What you can do is discover
whether an instance is of one of the types from a predefined (at compile
time) set. For example:

Base& x = ... // Gen element from the choice. 

if (DerivedA* a = dynamic_cast<DerivedA> (&x))
{
  // It is DerivedA.
}
else if (DerivedB* b = dynamic_cast<DerivedB> (&x))
{
  // It is DerivedB.
}

Other things that you could do are define a virtual function in Base
and then implement it in DerivedX (using type customization) or call
typeid() on the instance to get, for example, the type name.

Boris