I am creating a game where the first scene will have a generated map saved as a 2D array, then the next scene takes care of all the combat. Once that's done, user needs to go back to the first scene and see the same map. I have followed Unity's tutorial on Data persistence, and as you can see in the code below I am checking twice if an Instance is not null and destroying the object if its not.

The problem is, that every time I go back from combat scene to the map scene, it creates another instance of WorldMapManager, and generates another map on top of the existing one.

Where am I going wrong to stop creation of unnecessary extra copies of WorldMapManager object?

public class WorldMapManager : MonoBehaviour
{
    public static WorldMapManager Instance { get; private set; }
    public static int _mapSizeX = 4;
    public static int _mapSizeY = 4;
    public static int _playerScore;
    public static int _playerCells;
    public static int _enemyScore;
    public static int _enemyCells;
    public static GameObject[,] _map;
    public static GameObject _startingPoint;
    public static Vector2Int _playerBase;

    // Awake is called before Start
    void Awake()
    {
        if (WorldMapManager.Instance != null)
        {
            Destroy(gameObject);
        }
        else
        {
            DontDestroyOnLoad(gameObject);
        }
        SceneManager.sceneLoaded  = OnLevelFinishedLoading;
    }

    // Initialize the map
    public void InitMap()
    {
        // Map Generation happens here
    }

    // OnSceneLoaded is called when a scene is loaded
    void OnLevelFinishedLoading(Scene scene, LoadSceneMode mode)
    {
        if (scene.name == "WorldMap")
        {   
            if (WorldMapManager.Instance != null)
            {
                Destroy(this);
            } else
            {
                InitMap();
            }
        }
    }
}

I have been stuck on this for several days trying different approaches, but I'm all out of ideas, so thank you very much for any help.

CodePudding user response：

By the looks of your code it seems you never ever set the WorldMapManager.Instance. So it will always be null and always go on to DontDestroyOnLoad(gameObject);.

So add the assignment to Instance too.

Instance = this;
DontDestroyOnLoad(gameObject);

For the same reason in void OnLevelFinishedLoading(Scene scene, LoadSceneMode mode) the InitMap() will be executed. No need to set anything to Instance here ofcourse.