Unity is reseting Dictionary when game is playing

Question

I have a class named Item, I am storing instances of this class in list. List is created before game starts, everything works fine in that moment but when I am playing, items still are in list but components Dictionary in each seems to be reset because it haven't got any elements, before game it has.

This is my Item class:

[Serializable]
public class Item
{
    public string Name { get; }

    private Dictionary<Type, ItemComponent> components = new Dictionary<Type, ItemComponent>(); 

    public comp GetItemComponent<comp>() where comp : ItemComponent
    {
        Debug.Log(components == null); //in game shows true

        return
             components.Values.OfType<comp>().FirstOrDefault();
    }

    public Item AddItemComponent(ItemComponent component)
    {
        components.Add(component.GetType(), component);
        return this;
    }

    public Item(string name, string imagePath)
    {
        //components = new Dictionary<Type, ItemComponent>();

        Name = name;
        ImagePath = imagePath;
    }

}

I am not reset or changing items during game.

What could be the problem? Is it connected with Unity serialization limitations?

Answer 1

In Unity, Dictionaries are not serialized out of the box, so if they were populated in the Editor, they become cleared when the game starts.

You will want to run your AddItemComponent method at runtime as necessary to repopulate your Dictionary.

There might be plugins around to help make Dictionaries serializable (or at least classes similar to Dictionary), but you'd have to look around. Check this thread too.

Answer 2

You may be able to make the dictionary static in order to prevent it from being cleared!

I spent a day and a half looking for a fix to this, and found tons of unresolved issues, and no definitive answer online or from a few AIs. Still not sure why the dictionary gets cleared (I created mine in Start()) so if anyone knows more about this, please share!

My dictionary that was magically cleared the frame after being created in a MonoBehaviour:

void ReadTilemapToDict()
{
    foreach (Vector3Int pos in 
    StructureTilemap.cellBounds.allPositionsWithin)
    {
        if (StructureTilemap.HasTile(pos))
        {
            var tileInMap = StructureTilemap.GetTile(pos);
            if (tileInMap is RuleTileWithData ruleTileWithData)
            {
                // Add the tile's data to the dictionary
                _TileStatsDict.Add(pos, new TileStats 
                { 
                    tile = tileInMap, 
                    gridPos = pos, 
                    maxHealth = ruleTileWithData.health,
                    health = ruleTileWithData.health,
                    structure = ruleTileWithData.structure,
                    corpsePrefab = ruleTileWithData.corpsePrefab,
                    hitEffects = ruleTileWithData.hitEffects
                });
            }
        }
    }
}