Best Practice For List of Polymorphic Objects in C++

Question

What is a common practice for the storage of a list of base class pointers each of which can describe a polymorphic derived class?

To elaborate and in the interest o

Answer 1

I would propose boost::shared_pointer in an STL container. Then use dynamic_cast to downcast guarantee type correctness. If you want to provide helper functions to toss exceptions instead of returning NULL, then follow Alex's suggestion and define a template helper function like:

template 
T* downcast_to(U *inPtr) {
    T* outPtr = dynamic_cast(inPtr);
    if (outPtr == NULL) {
        throw std::bad_cast("inappropriate cast");
    }
    return outPtr;
}    

and use it like:

void some_function(Shape *shp) {
    Circle *circ = downcast_to(shp);
    // ...
}

Using a separate class like GenericShape is just too strongly coupled with every class that descends from Shape. I wonder if this would be considered a code smell or not...