Took me a second but I think I see what is going on here with the base
class. I can see where that could be a nightmare in maintenance.I
grabbed a couple of .h files fromhttp://ootips.org/yonat/4dev/that
should help.
Consider using boost's shared_ptr instead
Another question - say I was to use this example, would my class
declarations go inside the braces in the statement
class Weapon : public Item { /*in here?*/ }; ?
yes, keep in mind that different parts of your hierarchy will have
their own attributes and responsabilities. Example: an AssaultRifle
is_a type of Weapon which is_a type of Item.
Like I said, I am actually just about to jump into classes. I also
assume that I would do that for any class inheriting the public parts of
class Item (i.e. any items).
Not really. Consider that all items have a weight/mass. Item's
derivatives need not handle that aspect so you'ld keep weight in Item,
no virtual getweight() function needed. Weapon might itself become a
base class for concrete weapons (ie, rifle, laser, grenade, etc). All
weapons can fire() but each weapon fires in its own way. A rifle might
have an ammo count. And so on. See if the code below clarifies some
issues, i'm completely ignoring the fact that an Item needs to be
loaded/equipped.
Note how lifetimes are greatly simplified by the use of
boost::shared_ptr.
#include <iostream>
#include <vector>
#include <string>
#include <boost/shared_ptr.hpp>
class Item {
double weight;
protected:
Item(double w = 0.0) : weight(w) { }
public:
~Item() { std::cout << "~Item()\n"; }
double getweight() const { return weight; }
virtual void use() = 0;
};
class Weapon : public Item
{
protected:
Weapon(double w = 0.0) : Item(w) { }
virtual void fire() = 0;
};
class AssaultRifle : public Weapon
{
int ammo;
public:
AssaultRifle(int a = 16) : Weapon(20.1), ammo(a)
{
std::cout << "AssaultRifle()\n";
}
~AssaultRifle() { std::cout << "~AssaultRifle()\n"; }
void use()
{
fire();
std::cout << "fired!, ammo left :" << ammo;
std::cout << std::endl;
}
private:
void fire() { --ammo; }
};
int main()
{
typedef boost::shared_ptr< Item > SPtrItem;
std::vector< SPtrItem > inventory;
inventory.push_back( SPtrItem( new AssaultRifle(32) ) );
std::cout << "inventory[0]'s weight is: ";
std::cout << inventory.at(0)->getweight();
std::cout << std::endl;
inventory.at(0)->use(); // universal Item user
}
/*
AssaultRifle()
inventory[0]'s weight is: 20.1
fired!, ammo left :31
~AssaultRifle()
~Item()
*/
