C++ Programming: A Practical Approach

Dynamic Polymorphism 283

of classes MetalShape,CuboidMetal defined in Program 6.3, we can implement runtime poly-

morphism as follows:

MetalShape* ptr=new CuboidMetal( ); // Storing address of derived class object into base class pointer

// is upcasting.

ptr

-

>DeterminePurity(); // Call to overridden function

When the address of a derived class object is stored into a base class pointer, it is known as

upcasting. When the address of a base class object is assigned to a derived class pointer, down-

casting occurs.

CuboidMetal* ptr=new MetalShape(); // This will not compile.

When a derived class object is assigned to a base class object, the ...