Base to derived cast

[Kyon]

Heya, I'm just curious. Is there such a cast, that a base class (pointer) could be casted to a derived class (pointer), in which the base data members are maintained and the derived are declared via the default constructor? If not, how would this be possible with basic templating?

[Disch]

You cannot change an object's type. Once you create an object of a specific type, it be that type until it is destroyed.


The only way to do what you're suggesting would be something like this:

Base* p = new Base;

// now we want to convert that to a 'Derived'
// we can't turn the above object into a Derived.  The best we can 
//  do is create a new object:

Derived* d = new Derived( *p );

// and reassign:

delete p;
p = d;