Efficient C++ Performance Programming Techniques

Virtual Function Mechanics

If you really wanted to avoid virtual functions, you could emulate dynamic binding by providing your own type resolution code. Suppose you are maintaining a class hierarchy of zoo animals [Lip91], where ZooAnimal is your base class:

class ZooAnimal {
public:
    ...
    virtual void draw();
    int resolveType() {return myType;}
private:
    int myType;
    ...
}

The rest of the animals in the zoo are derived from ZooAnimal. The resolveType() method will enable you to distinguish a Bear from a Monkey at run-time.

class Bear : public ZooAnimal {
public:
    Bear (const char *name) : myName(name), myType(BEAR) {}
    void draw();
    ...
};

Each animal sets its appropriate type in its constructor.

If you wanted to draw all animals in the zoo, you ...