[SOLVED] How to make one object type for different subclasses with scriptable objects?

Unity Engine
1

Hi guys, I still not found answer on my question, I still not found way how to make it clear and easy.

I have some scriptable objects, for example: wood, iron, shovel.

Basic item class

public class Item : ScriptableObject
{
    public int itemID;
    public enum itemTypes
    {
        Resource,
        Product,
        Machine
    }
    public itemTypes itemType;
    public string itemTitle;
    public Sprite itemIcon;
    public int itemValue;
    public double weight = 0;

    public virtual void Use()
    {
        Debug.Log("You touch " + itemTitle);
    }

}

Product (shovel) item class

public class Production : Item
{
    public double priceSell;
    public List<Item> prodList = new List<Item>();

    public Inventory inventory;

    private void Awake()
    {
        GameObject gameObject = GameObject.Find("Inventory");
        inventory = gameObject.GetComponent<Inventory>();
    }

    public override void Use()
    {
        base.Use();

        Debug.Log("ItemID: " + itemID);
       Item item = inventory.GetItemByID(itemID);
       if (inventory.CheckItem(item))
        {
            Debug.Log("You have this item " + itemTitle);
        }
       else
        {
            Debug.Log("You haven't " + itemTitle);
        }
    }
}

I can’t check item in iventory, because inventory work with base Item class, it want Item type object for do functions.
For example part of Inventory.cs

public Item GetItemByID(int itemID)
    {
        Debug.Log("GetItemByID called, itemID: " + itemID);
        return factoryItems.Find(x => x.itemID == itemID);
    }

    public bool CheckItem(Item item)
    {
        Debug.Log("Check item function called!");
        return factoryItems.Exists(x => x == item);
    }

Inventory hold all items with Item object type and use List for that. But my items doesn’t have Item object type, they are Resource(wood, iron) and Product(shovel) item types. I know two ways how to solve it, but I don’t like anyone.

  1. Remove item subclasses and make all items like Item, use enum to get itemType and then use switch for each type when I want to Use() it - I don’t like this, because a lot of null variables will be for each item, for example I use List prodList for item recipe/blueprint(only Product items need this), simple wood doesn’t need this variable at all.
  2. Use it at is, but also with enum and check itemType with if and switch. - I lot of hard and massive logic in code, easy way to make problems for self.

Give me advice please how I can work with any item type in my inventory?

2

I’m not 100% sure what you want, it seems you forgot to ask your question, but does this help?

public abstract class Item : ScriptableObject
{
    public abstract bool IsProduct { get; }
}

public class ItemProduct : Item
{
    public override bool IsProduct { get { return true; } }
}

public class ItemResource : Item
{
    public override bool IsProduct { get { return false; } }
}

Item item = ...;
if (item.IsProduct) item.Use();
3

Thanks, but it doesn’t :slight_smile:

Problem in object’s types, Inventory script hold all items as Item, but actually some of them are Resource and some are Product.

So when script ask Invetory to CheckItem(item), I got NullPointReference, because as I think, script can’t use Resource/Product type, it know only Item type.

So main question is, how I can attach parent class type for child class objects? If all this object are scriptable and has one parent class.

4

So you are trying to cast the items to the Resource/Product type, but sometimes that results in a null pointer, since the Item in question is not of that type. Then I see a few options:

  • Do a check first:
if (!(item is Product)) return;
  • Add the check in the root class, as I described above:
if (!item.IsProduct) return;
  • Do a null check after the cast:
Product product = (Product)item;
if (product == null) return;

If you want to make things a little more flexible, you could do essentially the same, but use interfaces for the check:

public class Product : Item, IProduct
if (!(item is IProduct)) return;

That way you can have different subclasses implement the same interface and still only require one check. Also, a single subclass could implement multiple interfaces.

In your case I can imagine this to be an interface for example:

public interface IPrice
{
    public double PriceSell { get; }
}

On a side note, don’t store prices as floating point values, use an integer with fixed point representation instead. (Store as int in cents, half the memory, none of the rounding problems.)

5

I got it work, but I don’t understand logic actually.

My inventory script is instance

public static Inventory instance;

    private void Start()
    {
        instance = this;
        UpdatePanelSlots();
    }

First mistake was get Inventory component

private void Awake()
    {
        GameObject gameObject = GameObject.Find("Inventory");
        inventory = gameObject.GetComponent<Inventory>();
    }

In subclass scripts, that code is useless.

Al I need is call
Inventory.instance.CheckItemByID(itemID) and it works. Maybe I don’t understand object types for scripable objects…

For now I use:

public override void Use()
    {
        base.Use();

        Debug.Log("Try to get item " + itemID);
        Item item = Inventory.instance.GetItemByID(itemID);
        if(item)
        {
            Inventory.instance.AddItem(item);
        }

    }

I still have problems, if item not in inventory, script can’t found it. But this is just question of time. I need to improve it with some ItemsManager or something…

Thanks for your help and sorry for my stupidity :wink: