pure virtual functions....

[GSXdan]

Say i have a base class, Square, which goes to child class Property, which has 3 child classes Hall, Eatery, and NonProp. if i declare a pure virtual function, action, in Square, do i need to override it in Property even if i have no use for it there? I would just implement it in Property, but my prof said to do it in the Square class, since we are going to expand on this later.

and if i do need to override it in Property, can i just make it a empty function?

thanks ^dan

[doctorgonzo]

If a class has a pure virtual function, it is an abstract class. It can't be instantiated. If your provide a pure virtual function in Square, and don't override it in Property, then Property too will become an abstract class that can't be instantiated. That's not a problem if you never need to actually create a Square or Property object.

[GSXdan]

Yea they only need to be instantiated in Hall, Eatery, and NonProp, so i just used the code:

virtual void action(Person *);

i havent compiled yet, but my prof said that would be fine.

thanks

[doctorgonzo]

That's not a pure virtual function. You need to add an =0 to the end.

[GSXdan]

Yea, the pure virtual function is in the base class square. sorry for the confusion. here is what the h file looks like:

#ifndef SQUARE_H
#define SQUARE_H


// base class Square
class Square {

        public:
                Square(string= NULL, int=0);
                virtual void action(Person *) = 0;
                virtual ~Square() { };


        protected:
                string Sname;
                int Sloc;




};



//  class Property, inherits from Square
class Property : public Square {

        public:
                Property(string , int , int);

        protected:
                int CostToBuy;
                bool IsOwned;
                Person * WhoOwns;
};



// class Hall, inherits from Property
class Hall : public Property {

        public:
                Hall(string, int, int, int, int, int, int);
                virtual void action(Person *);

        protected:
                int CostPerRoom;
                int MaxRooms;
                int InitRentCost;
                int RentCostPerRoom;
                int ActNumRooms;




};



// class Eatery, inherits from Property
class Eatery : public Property {

        public:
                Eatery(string, int, int, int) ;
                virtual void action(Person *);

        protected:
                int CostToEat;

};




// class NonProp, inherits from Square
class NonProp : public Square {

        public:
                NonProp(char, string, int);
                virtual void action(Person *);

        protected:
                char npType;

};



#endif

thanks

[doctorgonzo]

That looks like it should work just fine.

[HNPFL]

I could learn a thing or 2 from u guys about C++