O my god, a Persistent Object!

Many people are terrified by the concept of a persistent object.

The concept is really quite simple.

Consider this:

class body {

public:

inline virtual char* identify() const =0;

inline virtual float GetVolume() const =0;

inline virtual float GetSurface() const =0;

};

#include "body.h"

class cylinder : public body {

public:

cylinder (float,float);

virtual char* identify() const;

virtual float GetVolume() const;

virtual float GetSurface() const;

protected:

// a cylinder is described by

// its radius and height

float radius;

float height;

};

#include "body.h"

class cube : public body {

public:

cube (float);

virtual char* identify() const;

virtual float GetVolume() const;

virtual float GetSurface() const;

protected:

// a cube has just one length to

// fully describe it...

float length;

};

And that’s the data portion of these classes.

That’s what you would have to store in a file in order to re-create these objects.

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