xna - How should I handle collectable/droppable/stackable items in an inventory?

I am working on a game with an inventory system, but am trying to figure out the best way of doing it. I have read the post about adding WorldItems or InventoryItems to a list, which is fair enough and I figured that out myself anyway.

However, perhaps I add two SwordItems to this list (for example). I want the game to show that I have quantity 2 of these, not two individual items. What is the best way to achieve this with a List based inventory structure. I think I saw a GroupBy method, where I could GroupBy item type Sword. Is this a good way to achieve this? Or can you suggest a better alternative?

Answer

Build your inventory as a list of item stacks, and not items. Individual items (or items that cannot be stacked) are simply a stack of one. For example:

class ItemStack {

  Item item;
  int count;

  // ...public methods here...
}

This allows you to treat your inventory as a simple homogeneous List or similar, and also allows you the flexibility to support multiple stacks of a particular item -- for example, you can support splitting a stack of items in this system, whereas in one where you tried to GroupBy() might get pretty cumbersome.

It will require a little more work on your part to deal with consumption of items or their removal from the stack, but it's not that big of a deal.