How do I remove a specific element from a list?

[Chuka4Cheese]

Hi. I am currently making a saving system for my grid-based inventory. I will try to explain how it works now.
I decided to do it by creating several lists. They hold item Id, item quantity, item position on X axis, item position on Y axis and a bool “rotated” which turns on if the item is rotated on the grid.(see picture *1)

Whenever I pick up an item I remove this item’s data from a list and whenever I place an item I add it.

    private void PlaceItem(Vector2Int tileGridPosition)
    {
        bool successfullyPlacedItem = selectedItemGrid.PlaceItem(selectedItem, tileGridPosition.x, tileGridPosition.y);
        if (successfullyPlacedItem)
        {
            selectedItemGrid.storedItemsId.Add(selectedItem.itemData.itemId);
            selectedItemGrid.storedItemQuantityList.Add(selectedItem.itemAmount);
            selectedItemGrid.storedItemPosXList.Add(selectedItem.onGridPositionX);
            selectedItemGrid.storedItemPosYList.Add(selectedItem.onGridPositionY);
            selectedItemGrid.storedItemRotatedBoolList.Add(selectedItem.rotated);
           
            selectedItem = null;
            rectTransform.SetAsLastSibling();
        }
    }

    private void PickUpItem(Vector2Int tileGridPosition)
    {
        selectedItem = selectedItemGrid.PickUpItem(tileGridPosition.x, tileGridPosition.y);
        if (selectedItem != null)
        {
            selectedItemGrid.storedItemsId.Remove(selectedItem.itemData.itemId);
            selectedItemGrid.storedItemQuantityList.Remove(selectedItem.itemAmount);
            selectedItemGrid.storedItemPosXList.Remove(selectedItem.onGridPositionX);
            selectedItemGrid.storedItemPosYList.Remove(selectedItem.onGridPositionY);
            selectedItemGrid.storedItemRotatedBoolList.Remove(selectedItem.rotated);
            rectTransform = selectedItem.GetComponent<RectTransform>();
            rectTransform.SetAsLastSibling();
        }
    }

I then save data from those lists to a .json file.

    [System.Serializable]
    public class InventoryDataStr
    {
        public List<int> itemIdList;
        public List<int> itemAmountList;
        public List<int> itemPosXList;
        public List<int> itemPosYList;
        public List<bool> itemRotatedBoolList;
    }


    public class InventorySaveSystem : MonoBehaviour
    {

        public void SaveInventory()
        {

            InventoryDataStr saveData = new InventoryDataStr();
            saveData.itemIdList = ItemGrid.instance.storedItemsId;
            saveData.itemAmountList = ItemGrid.instance.storedItemQuantityList;
            saveData.itemPosXList = ItemGrid.instance.storedItemPosXList;
            saveData.itemPosYList = ItemGrid.instance.storedItemPosYList;
            saveData.itemRotatedBoolList = ItemGrid.instance.storedItemRotatedBoolList;

            string json = JsonUtility.ToJson(saveData);
            string filepath = Application.persistentDataPath + "/playerInventory.json";
            System.IO.File.WriteAllText(filepath, json);
            Debug.Log(filepath);
       
        }

When i want to load the inventory i first load lists data from .json file

    public void LoadInventory()
        {
            string filepath = Application.persistentDataPath + "/playerInventory.json";
            string json = System.IO.File.ReadAllText(filepath);
            InventoryDataStr saveData = JsonUtility.FromJson<InventoryDataStr>(json);

            ItemGrid.instance.storedItemsId = saveData.itemIdList;
            ItemGrid.instance.storedItemQuantityList = saveData.itemAmountList;
            ItemGrid.instance.storedItemPosXList = saveData.itemPosXList;
            ItemGrid.instance.storedItemPosYList = saveData.itemPosYList;
            ItemGrid.instance.storedItemRotatedBoolList = saveData.itemRotatedBoolList;

            ItemGrid.instance.UpdateInventory();
        }
    }

    public void UpdateInventory()
    {
        inventoryController.CreatePrefabForLoading();
    }

Then I create item prefab and assign it data that i take from saved lists. After that I place it on the grid.

    public void CreatePrefabForLoading()
    {

        for (int i = 0; i < selectedItemGrid.storedItemsId.Count; i++)
        {
            InventoryItem inventoryItem = Instantiate(itemPrefab).GetComponent<InventoryItem>();

            rectTransform = inventoryItem.GetComponent<RectTransform>();
            rectTransform.SetParent(canvasTransform);
            rectTransform.SetAsLastSibling();
            rectTransform.localScale *= selectedItemGrid.inventoryCanvas.rootCanvas.scaleFactor;

            foundItem = selectedItemGrid.database.Items.Find(e => e.itemId == selectedItemGrid.storedItemsId[i]);
            inventoryItem.Set(foundItem);

            inventoryItem.itemAmount = selectedItemGrid.storedItemQuantityList[i];
            inventoryItem.onGridPositionX = selectedItemGrid.storedItemPosXList[i];
            inventoryItem.onGridPositionY = selectedItemGrid.storedItemPosYList[i];
            inventoryItem.rotated = selectedItemGrid.storedItemRotatedBoolList[i];
            inventoryItem.RotateForLoading();

            inventoryItem.UpdateItemAmount();
            selectedItemGrid.PlaceItem(inventoryItem, selectedItemGrid.storedItemPosXList[i], selectedItemGrid.storedItemPosYList[i]);
        }
    }

The problem arises when i’m starting to pick up items with the same data (having the same position on an axis, having the save item amount, e.t.c.).
Since I’m using List.Remove command it removes the first element that matches selected item’s data.
How would I make it so that when I pick up an item it would remove that item’s data from the list instead of removing the first element that matches that data?

[spiney199]

The issue here is you have spread the information on an item across multiple lists, when instead you should have all that information bundled up in an object, and have a list of said object instead.

In case you aren’t aware, you can serialise regular C# classes and structs for use in the inspector: Unity - Scripting API: Serializable

With inventory systems, generally you will need to be generating unique ID’s for items that are being instances into the game world to be able to differentiate them all from one another.

[Chuka4Cheese]

@spiney199

The issue here is you have spread the information on an item across multiple lists, when instead you should have all that information bundled up in an object, and have a list of said object instead.

In case you aren’t aware, you can serialise regular C# classes and structs for use in the inspector: https://docs.unity3d.com/ScriptReference/Serializable.html

With inventory systems, generally you will need to be generating unique ID’s for items that are being instances into the game world to be able to differentiate them all from one another.

Thanks for the comment. If I understood you correctly I need to find a way to create unique Guid for my item gameobjects and serialize the list of item gameobjects(with data that i need to serialize being put in a struct inside that gameobject(Guid, item position on the grid, item amount, rotated bool)). This way when I reboot the game\editor my items that I saved would still have their unique id. Then for loading I would just need to instantiate each item in that list and put them in correct spots on my grid using that item’s data. And when I’m picking up\placing an item I would have to remove\add that item to the list. I’m asking because I tried making a list of my item gameobjects before but I failed because whenever I rebooted the game\editor item’s reference id got reset so I would have a list full of missing references.

[spiney199]

You can’t serialise any UnityEngine.Object’s to disk, nor can you serialise references to them.

You can only serialise plain data. Your items (whether they be scriptable objects or prefabs) will need their own IDs, so you can look from a simple database of yours, and then rebuild the runtime game state from your pure data representation. Ideally an inventory/item system takes a model/view approach, where the state of all items and inventories, etc, is completely separate from the the actual game object side of things.

[Chuka4Cheese]

Alright, so I reworked how my inventory system works. Instead of saving item info in several lists I save it in 1 list (see picture *1) that contains “Item” class with all the info that I need to save. (see picture *2)

When I’m picking up an item I remove this item’s class from the list and when I’m placing an item I update class with new info about said item and then add it to the list. (see picture *3)

I also had to change how inventory save system works. Now it saves list that has all item info. (see picture *4)

And here’s how CreatePrefabForLoading function looks now. It goes through the list of and assigns that info to a newly created prefab. (see picture *5)

So far everything works perfectly, thanks a lot for the help!
If I find a bug with this new system I’ll try to fix it and post solution here.