16. Implementing prototypes

class AbstractItem {
public:
    virtual AbstractItem* clone() = 0;
    //...

};//class AbstractItem

class RealItemA : public AbstractItem
{
public:
    virtual AbstractItem* clone();
    //...

};//class RealItemA

class RealItemB : public AbstractItem
{
public:
    virtual AbstractItem* clone();
    //...

};//class RealItemB

Prototype details:

• Provides mechanism for virtual construction.

• Instantiation of prototypes is deferred:

  • new prototypes can be instantiated dynamically at runtime

  • it is possible to delete existing prototypes.

We might also consider maintaining a registry of prototypes:

    std::map< std::string, AbstractItem* > item_registry;