Item functionality with database

Question

So the game i'm making will have items with different functionality such as ammo boxes, med-packs, guns, food, water ect. My problem is i don't know where to put the code for the specific functionality e.g code for eating food.

My item system works by having a database (dictionary with a string and item stats) and an inventory list of strings. When using a item i look up the stats of that item using the string in the inventory list.

One idea i had was to have scrips on the player something like heal, ammo, gun ect, and have methods in those scrips for the functionality. Is this a good way of doing it?

Answer 1

Part of an item's stats can include a reference to the behavior of the item when it is consumed or used. This can be represented in the item's structure as a delegate/function pointer/closure/et cetera based on language.

In C#, you could do it with an Action delegate. So your item structure would look like:

class Item {
  int value;
  int weight;
  // ...other stats...

  Action<Item, Character> onUseEffect;
};

onUseEffect is a (possibly-null) reference to a function that takes an Item and a Character, which at runtime will be the item being used and the character using the item, respectively. You can naturally have more (or fewer) parameters as needed.

So now, when using an item you look up it's Item object as you do now to get the stats of the item. And if that Item has a non-null onUseEffect, you call that function:

void UseItem(string name) {
  Item item = m_itemDatabase[name]; // look up the item...
  if (item.onUseEffect != null) {
    item.onUseEffect(item, thisCharacter);  // use the item...
  }
}

You'd bind these actions when you create each item in the database:

Item potionItem = new Item();
// ...other initialization...
potionItem.onUseEffect = (item, user) => { 
  // Potions heal 50 HP for the user.
  user.Health += 50;
};

m_itemDatabase.Add("Potion", potionItem);

All of this allows you to define your item behavior in code without having to subclass Item for each new type or behavior. It's also a useful building block towards allowing your item's behavior to be defined in scripts (the onUseEffect delegate simply becomes a call to the item's script), as you proposed in your question. Using scripts (e.g., data) to describe the behavioral effects of your items is a good idea in general, although it might be overkill depending on the size of your game and data set. And whether or not you already have a scripting mechanism built.