[xsd-users] polymorphism through xs:choice

[Bielik, Robert]

One option would be if there is a possibility to assign a GUID to the generated C++ type, and map that GUID to a casting function. I do the last bit today in my code, but I'd be happy to have the GUID be generated via XSD, so that C# clients can send objects to C++ servers.

Would that be simple to do via XSD -> CodeSynthesis ?

Regards,
/Rob

-----Original Message-----
From: xsd-users-bounces at codesynthesis.com [mailto:xsd-users-bounces at codesynthesis.com] On Behalf Of Boris Kolpackov
Sent: den 11 juni 2013 14:52
To: Harg Tholan
Cc: xsd-users at codesynthesis.com
Subject: Re: [xsd-users] polymorphism through xs:choice

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