Dynamic Cast 2.cpp

//dyncast2.cpp
//tests dynamic casts
//RTTI must be enabled in compiler
#include <iostream>
#include <typeinfo> //for dynamic_cast
using namespace std;
////////////////////////////////////////////////////////////////
class Base
{
protected:
    int ba;
public:
    Base() : ba(0)
    { }
    Base(int b) : ba(b)
    { }
    virtual void vertFunc() //needed for dynamic_cast
    { }
    void show()
    {
        cout << "Base:ba=" << ba << endl;
    }
};
////////////////////////////////////////////////////////////////
class Derv : public Base
{
private:
    int da;
public:
    Derv(int b, int d) : da(d)
    {
        ba = b;
    }
    void show()
    {
        cout << "Derv:ba=" << ba << ", da=" << da << endl;
    }
};
////////////////////////////////////////////////////////////////
int main()
{
    Base* pBase = new Base(10); //pointer to Base
    Derv* pDerv = new Derv(21, 22); //pointer to Derv
//derived-to-base: upcast -- points to Base subobject of Derv
    pBase = dynamic_cast<Base*>(pDerv);
    pBase->show(); //"Base: ba=21"
    pBase = new Derv(31, 32); //normal
//base-to-derived: downcast -- (pBase must point to a Derv)
    pDerv = dynamic_cast<Derv*>(pBase);
    pDerv->show(); //"Derv: ba=31, da=32"
    return 0;
}