CODEWITHSUNDEEP
c++arrayspointersdynamicinventory
Zach King
Zach King

Reputation: 1218

C++ Dynamic Inventory System--Adding/Removing Items

Ok, so I have a text-driven game in C++. I've written a Hero class. I also wrote a base class called Item and a subclass of that called Weapon (the idea is to have Weapons, Potions, QuestItems, etc. that inherit from the Item class). That way I can make my "Hero" have an instance variable inventory of Items. I wanted this to be dynamic in case the Hero gained upgrades for his/her storage space.

So my Hero class has a member/instance variable that is a dynamic array of pointers to Items. I declare this and then loop through it setting each element to a new Item like so:

Item** inventory = new Item*[15];
for (int i = 0; i < 15; i++)
    inventory[i] = new Item();

That took place in the Hero class's void Init() function which all the constructors call (flexible construction). Now then, I have tried to write a member function to add an item to the first "empty" slot in the inventory, but that is pretty gritty and couldn't figure out what was crashing my program when I tested it. Ultimately I figured out it was crashing when I tried to access an element of the array. Now I just have this snippet that assumes the first element is empty and tries to "add" the item given to that index in the array:

void Hero::AddToInventory(Item *item)
{
    *inventory[0] = item;
}

And here is how I called the method in main():

int main()
{
    Hero *player = new Hero("Joe");
    Item *primaryWeapon = new Item("Dagger");
    player->AddToInventory(primaryWeapon);
    return 0;
}

Any help is greatly appreciated; I'm just a little rusty on my dynamic objects and data structures in C++. Thanks in advance!

P.S. I know this can be done simpler with vectors but I have not learned how to use those yet and would like to stick with the dynamic arrays for now.

Upvotes: 0

Views: 2191

Answers (1)

Lochemage
Lochemage

Reputation: 3974

First of all, you leak memory by first initializing each array index with a new Item() and then replacing that allocated item with the actual item later. It is probably better to just have an array of null pointers to begin with.

Item** inventory = new Item*[15];
for (int i = 0; i < 15; i++)
    inventory[i] = NULL;

I believe you can also initialize an array to null like this:

Item** inventory = new Item*[15] = {NULL,};

Now, you say you have a subclass of Item called Weapon, but I see that you never use it. Once you declare new Item(), it is of type Item, no longer able to morph into derived class types like Weapon(). So, in this case, to create a dagger weapon, it should look more like this instead:

Item *primaryWeapon = new Weapon("Dagger");

Lastly, you get the crash during AddInventoryToItem because you are dereferencing your instance of Item at the given index, then assigning it to a pointer to an Item instead of to an Item directly. Try this instead:

void Hero::AddToInventory(Item *item)
{
    inventory[0] = item;
}

Also note that if you just simply replace the inventory index with a new pointer, you could also result in a memory leak. However, if each item was initialized to null instead of a new Item(), and you only added the item to an empty slot, this won't be a problem.

Upvotes: 1

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