Errors in console after changing execution order

[SweetMouse85]

Hello, so after changing the execution order in Unity a few errors appeared, please help.
What is going on?

Also no enemies are spawning at all at this point.

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class GridManager : MonoBehaviour
{
    [SerializeField] Vector2Int gridSize;

    [Tooltip("World Grid Size - Should match UnityEditor snap settings.")]
    [SerializeField] int unityGridSize = 10;
    public int UnityGridSize { get { return unityGridSize; } }

    Dictionary<Vector2Int, Node> grid = new Dictionary<Vector2Int, Node>();
    public Dictionary<Vector2Int, Node> Grid { get { return grid; } }

    void Awake()
    {
        CreateGrid();
    }

    public Node GetNode(Vector2Int coordiates)
    {
        if (grid.ContainsKey(coordiates))
        {
            return grid[coordiates];
        }

        return null;
    }

    public void BlockNode(Vector2Int coordinates)
    {
        if (grid.ContainsKey(coordinates))
        {
            grid[coordinates].isWalkable = false;
        }
    }

    public void ResetNodes()
    {
        foreach(KeyValuePair<Vector2Int, Node> entry in grid)
        {
            entry.Value.connectedTo = null;
            entry.Value.isExplored = false;
            entry.Value.isPath = false;
        }
    }

    public Vector2Int GetCoordinatesFromPosition(Vector3 position)
    {
        Vector2Int coordinates = new Vector2Int();
        coordinates.x = Mathf.RoundToInt(position.x / unityGridSize);
        coordinates.y = Mathf.RoundToInt(position.z / unityGridSize);

        return coordinates;
    }

    public Vector3 GetPositionFromCoordinates(Vector2Int coordinates)
    {
        Vector3 position = new Vector3();
        position.x = coordinates.x * unityGridSize;
        position.z = coordinates.y * unityGridSize;

        return position;
    }

    void CreateGrid()
    {
        for(int x = 0; x < gridSize.x; x++)
        {
            for (int y = 0; y < gridSize.y; y++)
            {
                Vector2Int coordinates = new Vector2Int(x, y);
                grid.Add(coordinates, new Node(coordinates, true));
            }
        }
    }
}

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Pathfinder : MonoBehaviour
{
    [SerializeField] Vector2Int startCoordinates;
    public Vector2Int StartCoordinates { get { return startCoordinates; } }

    [SerializeField] Vector2Int destinationCoordinates;
    public Vector2Int DestinationCoordinates { get { return destinationCoordinates; } }


    Node startNode;
    Node destinationNode;
    Node currentSearchNode;

    Queue<Node> frontier = new Queue<Node>();
    Dictionary<Vector2Int, Node> reached = new Dictionary<Vector2Int, Node>();

    Vector2Int[] directions = { Vector2Int.right, Vector2Int.left, Vector2Int.up, Vector2Int.down };
    GridManager gridManager;
    Dictionary<Vector2Int, Node> grid = new Dictionary<Vector2Int, Node>();

    private void Awake()
    {
        gridManager = FindObjectOfType<GridManager>();
        if(gridManager != null)
        {
            grid = gridManager.Grid;
            startNode = grid[startCoordinates];
            destinationNode = grid[destinationCoordinates];
           
        }

    }

    // Start is called before the first frame update
    void Start()
    {
        GetNewPath();
    }

    public List<Node> GetNewPath()
    {
        gridManager.ResetNodes();
        BreadthFirstSearch();
        return BuildPath();
    }

    void ExploreNeighbors()
    {
        List<Node> neighbors = new List<Node>();    

        foreach(Vector2Int direction in directions)
        {
            Vector2Int neighborCoords = currentSearchNode.coordinates + direction;

            if (grid.ContainsKey(neighborCoords))
            {
                neighbors.Add(grid[neighborCoords]);

            }

        }

        foreach(Node neighbor in neighbors)
        {
            if(!reached.ContainsKey(neighbor.coordinates) && neighbor.isWalkable)
            {
                neighbor.connectedTo = currentSearchNode;
                reached.Add(neighbor.coordinates, neighbor);
                frontier.Enqueue(neighbor);
            }
        }
    
    }

    void BreadthFirstSearch()
    {
        startNode.isWalkable = true;
        destinationNode.isWalkable = true;

        frontier.Clear();
        reached.Clear();

        bool isRunning = true;

        frontier.Enqueue(startNode);
        reached.Add(startCoordinates, startNode);

        while(frontier.Count > 0 && isRunning)
        {
            currentSearchNode = frontier.Dequeue();
            currentSearchNode.isExplored = true;
            ExploreNeighbors();
            if(currentSearchNode.coordinates == destinationCoordinates)
            {
                isRunning = false;
            }
        }
    }

    List<Node> BuildPath()
    {
        List<Node> path = new List<Node>();
        Node currentNode = destinationNode;

        path.Add(currentNode);
        currentNode.isPath = true;

        while(currentNode.connectedTo != null)
        {
            currentNode = currentNode.connectedTo;
            path.Add(currentNode);
            currentNode.isPath = true;
        }

        path.Reverse();

        return path;
    }

    public bool WillBlockPath(Vector2Int coordinates)
    {
        if (grid.ContainsKey(coordinates))
        {
            bool previousState = grid[coordinates].isWalkable;
            grid[coordinates].isWalkable = false;
            List<Node> newPath = GetNewPath();
            grid[coordinates].isWalkable = true;

            if(newPath.Count <= 1)
            {
                GetNewPath();
                return true;
            }
        }

        return false;
        
    }
}

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

[RequireComponent(typeof(Enemy))]
public class EnemyMover : MonoBehaviour
{
    [SerializeField][Range(0f, 5f)] float speed = 1f;

    List<Node> path = new List<Node>();

    Enemy enemy;
    GridManager gridManager;
    Pathfinder pathfinder;

    // Start is called before the first frame update
    void OnEnable()
    {
        FindPath();
        ReturnToStart();
        StartCoroutine(FollowPath());
    }

    private void Awake()
    {
        enemy = GetComponent<Enemy>();
        gridManager = FindObjectOfType<GridManager>();
        pathfinder = FindObjectOfType<Pathfinder>();
    }


    void FindPath()
    {
        path.Clear();
        path = pathfinder.GetNewPath();
    }

    void ReturnToStart()
    {
        transform.position = gridManager.GetPositionFromCoordinates(pathfinder.StartCoordinates);
    }

    void FinishPath()
    {
        enemy.StealGold();
        gameObject.SetActive(false);
    }

    IEnumerator FollowPath()
    {
         for(int i = 0; i< path.Count; i++)
         {
            Vector3 startPosition = transform.position;
            Vector3 endPosition = gridManager.GetPositionFromCoordinates(path[i].coordinates);
            float travelPercent = 0f;

                transform.LookAt(endPosition);


                while (travelPercent < 1f)
                {
                    travelPercent += Time.deltaTime * speed;
                    transform.position = Vector3.Lerp(startPosition, endPosition, travelPercent);
                    yield return new WaitForEndOfFrame();
                }

         }

        FinishPath();
    }
    
}
    

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class ObjectPool : MonoBehaviour
{
    [SerializeField] GameObject enemyPrefab;
    [SerializeField] [Range(0, 50)] int poolSize = 5;
    [SerializeField] [Range(0.1f, 30f)]  float spawnTimer = 1f;

    GameObject[] pool;

    private void Awake()
    {
        PopulatePool();
    }

    // Start is called before the first frame update
    void Start()
    {
        StartCoroutine(SpawnEnemy());
    }

    void PopulatePool()
    {
        pool = new GameObject[poolSize];

        for(int i = 0; i < pool.Length; i++)
        {
            pool[i] = Instantiate(enemyPrefab, transform);
            pool[i].SetActive(false);
        }
    }

    void EnableObjectInPool()
    {
        for(int i = 0; i < pool.Length; i++)
        {
            if(pool[i].activeInHierarchy == false)
            {
                pool[i].SetActive(true);
                return;
            }
        }
    }

    IEnumerator SpawnEnemy()
    {
        while (true)
        {
            EnableObjectInPool();
            yield return new WaitForSeconds(spawnTimer);
        }
    }
   
}

[Nina]

Hi,

NullReferenceException means that a reference (“link”) to an instance is missing. Double click on the error message to see to which line in your code it is referring. If you exposed a field in the Inspector, make sure that it’s not empty.

Have you already tried to add Debug.Logs to your code to see what is going on during runtime?

[bixarrio]

When changing the execution order, you have enabled ‘race condition mode’. What did you change the order to?

There is a possibility that Pathfinder executes before GridManager. In the Pathfinder.Awake() you are referencing GridManager and this may be before GridManager.Awake() executed, so GridManager.CreateGrid() has not executed yet. This means that there are no startNode and destinationNode in the grid yet, but you are trying to access these.

Hmmm. The highlighted error shows that destinationNode is null. What is the first error in the console?

[SweetMouse85]

What do you mean by ‘race condition mode’ ?

This is the first error in the console.

This opens by double clicking it.

This is how the execution order is changed.

This is what`s showing when I double click the other error messages.

[SweetMouse85]

This is showing after double clicking. Have posted the others below.

[bixarrio]

What are the dimensions of the grid? The first error says that it cannot find an entry in the grid for position (10, 6). So it breaks. From there, everything is broken

[SweetMouse85]

The dimensions i typed in was 10, 6. In the video is 9, 6 used.
But i changed it for me because i have my castle entrence at 10, 6 and not at 9, 6 like in the video, chaning the dimensions to 9, 6 gets all the errors away.

Here are two pictures, with the dimensions of 10, 6 and then 9, 6

I thought I was free to change the destination and start coordinates so it would just fit to my game.
Why changing the destination coordinates causes all the errors?

[bixarrio]

Can you show the GridManager inspector? Is your grid large enough?

[SweetMouse85]

I hope that is what you meant.
I think it is large enough?

[bixarrio]

It is not. We start counting at 0, so a 10x10 grid has values between 0 and 9 on each axis. (10, 6) does not exist in that grid because the highest position in a 10x10 grid is (9, 9)

[SweetMouse85]

You are right! I was looking at it the wrong way…uff the tile that is marked, I was seeing it for whatever reason as the coordinate i need to type in the inspector… so i typed 10, 6
But yes inside the inspector the grid is stated as 10, 10 so of course you are right!
Thank you so much for your help by the way!
Really appreciate it a lot!

Sometimes i am too fast and overlook things and then mistakes happen

[bixarrio]

For the marked tile (10, 6) is, in fact, the coordinates you must type. Your grid just isn’t big enough. You should try to match your grid to the map. Your map is 21x11, but the grid starts at 0,0 so you probably only need the parts where the units can actually move. Looking at your screenshots, it looks like 11x7 should do. That would put the 2 gates at the extremes of the grid (0,0) and (10,6) and allow the units to move anywhere in that area

[SweetMouse85]

Thank you, I will try this.