Items in static List()

Question

So I have a static item list which stores a few classes, and in those classes are variables such as "int ID", "string name", "string description", "int currentAmount", etc.

ItemDatabase.cs...

public static List<Item> Items

static void LoadItemData()
{
    Items.Add(new item);
    ...
}

I then have a separate item list which will have items added to it for use by the player.

Player.cs...

List<Item> playerItems;

Then in other classes, I have AddItem(int ID) methods:

void AddItem(int id)
{
    foreach (Item i in ItemDatabase.Items)
        if (i.ID == id)
            playerItems.Add(i);
}

I'm currently adding in entities that will make use of the same data. But when I modify the Item added to the playerItems, it modifies ItemDatabase.Items (Obviously, due to referencing).

I can't make the Item class into a struct, because I have other classes which derive from it. I need the "currentAmount" integer to be by value. Is there any way I can do this?

P.S., I've tried deep cloning, and that doesn't play nicely with my Item class.

Why doesn't cloning work? Seems like that's the solution. Can you shallow clone if you're just modifying value types (`string`,`int`)? — D Stanley, Feb 04 '15 at 20:16
@DStanley, I tried to do a deep clone, inserting [Serializable] attributes at the top of each class, however other classes that I don't have control of like Texture2D were giving me that. I also have other classes inside the Item class. Wouldn't they be set to null if I didn't do a deep copy? — Shyy Guy, Feb 04 '15 at 20:26
You don't _need_ to serialize to do a deep clone - serializing and deserializing is just one way. If you're not changing reference types then I would just do a shallow clone (either manually copying property vlaues or using [`object.MemberwiseClone`](https://msdn.microsoft.com/en-us/library/system.object.memberwiseclone%28v=vs.110%29.aspx) — D Stanley, Feb 04 '15 at 20:31
@DStanley, thank you so much. I tried MemberwiseClone, and it worked excellent. Do you mind putting that as an answer? — Shyy Guy, Feb 04 '15 at 21:36

score 1 · Answer 1 · answered Feb 04 '15 at 20:16

You need to separate out currentAmount. Since that value only makes sense in the context of a Player anyways, I would take that out of the Item class, and use a Dictionary<Item,int> to keep track of the inventory:

Dictionary<Item, int> inventory = new Dictionary<Item, int>();

void AddItem(int id)
{
    foreach (Item i in ItemDatabase.Items)
        if (i.ID == id)
            playerItems.Add(i, 0); //Or whatever count
}

score 1 · Accepted Answer · answered Feb 04 '15 at 21:43

Obviously you need to clone the objects if you want to change them without affecting the original. Serialization is one way to do a "deep clone" but as you have discovered not all types can be serialized.

If you are just modifying the first-level value type properties (not changing related item's values or references) you can use object.MemberwiseClone to create a shallow copy (copies of value types and references).

score 0 · Answer 3 · edited May 23 '17 at 10:26

I'm still not sure where you are modifying ItemsDatabase.Items (currentAmount as property of the Entity doesn't makes much more sense), but for current amount in your Inventory, I guess this will help you:

Dictionary<Item, int> inventory = new Dictionary<Item, int>();

void AddItem(int id)
{
    foreach (Item i in ItemDatabase.Items)
        if (i.ID == id)
            {
              if(!inventory.Keys.Contains(i)){iventory.Add(i, 0);}
              inventory[i]+=1; //increment the amount of items in inventory.
            }
}

Important:

Dictionary uses Hash to get the object from dictionary, so, you probably want to override that method in your Item class:

class Item {
    public string Name;
    public string Description;
    public int currentAmount;

    public override int GetHashCode(){
       return Name.GetHashCode() + Description.GetHashCode();
    }
}

see more:

score 0 · Answer 4 · answered Feb 04 '15 at 20:31

0

do this:

void AddItem(int id)
{
    var item = ItemDatabase.Items.FirstOrDefault(x=> x.ID == id);
    if(item!=null){
        playerItems.Add(new Item(){ ID = item.ID, Name = item.Name, etc... })
    }
}

answered Feb 04 '15 at 20:31

aleha_84

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Items in static List()

4 Answers4