Thread: Polymorphism

Hello,

PHP Code:

//[CODE]

/*-------- Item Class --------*/
class Item
{
 protected:
     string name;
     int price;
     int useLevel;

 public:
     Item(string tname, int tprice, int tuseLevel);
     ~Item();

     string getName();
     int getPrice();
     int getUseLevel();
     virtual char getType();
     virtual int getDamage()=0;
     virtual bool isTwoHanded()=0;
     virtual int getProtection()=0;
};


/*-------- Weapon(Item) Class --------*/
class Weapon : public Item
{
 private:
     int causeDamage;
     bool twoHand;

 public:
     Weapon(string tname, int tprice, int tuseLevel ,int damage, bool twohands);
     ~Weapon();

     int getDamage();
     bool isTwoHanded();
     char getType();
};


/*-------- Armor(Item) Class --------*/
class Armor : public Item
{
 private:
     int protection;

 public:
     Armor(string tname, int tprice, int tuseLevel ,int tprotection);
     ~Armor();

     int getProtection();
     char getType();
};

//[/CODE] 


Item class is a base abstract class. Both Weapon and Armor are derived class. As far as i can remember the above is legal, but when the code goes like this

Code:

Item *equipedWeapon = new Weapon("Wooden Stick", 0, 1, 5, false);
Item *equipedArmor = new Armor("Shirt", 0, 1, 2);

MS VS compiler produces :
error C2259: 'Weapon' : cannot instantiate abstract class
error C2259: 'Armor' : cannot instantiate abstract class

Following the error code i came up to this which doesn't explain why i have to define the functions of Armor also in Weapon class and vice versa.

Originally Posted by anon

You need to override all pure methods (=0) if you want to instantiate those.

I can't see the point of overriding (for example) the getProtection() function in Weapon class.
It can lead to chaos for deep inheritance.

Anyway, thank you.

It really doesn't make sense to me right now (more than two years away from oop), because i can't see reuseability.