Bdtjtk

I have two objects: Tile and TileGrid which have their own scripts.
TileGrid can generate a 2d array of Tiles. Then I am trying to attach every Tile around the Tile in the script for every Tile, so all of my Tiles will have a reference to their 'neighbors'. I use a dictionary.
To do that I wrote a function which is accessing TileGrid's 2d array of Tiles.
Unfortunately, a NullReferenceException is thrown.

TileGridScript.cs

public class TileGridScript : MonoBehaviour

{

    public GameObject tileGrid;

    // Other properties ...

    public void MakeGrid(int width = 64, int height = 64)

    {

        tileGrid = new GameObject[width];

        for (int x = 0; x < width; x++)

        {

            tileGrid[x] = new GameObject[height];

            for (int y = 0; y < height; y++)

            {

                // !!! Instantiating tiles !!!

                tileGrid[x][y] = Instantiate(grassPrefab, new Vector2(x - width / 2, y - height / 2), Quaternion.identity);

            }

        }

        // !!! Call the function to connect Tiles !!!

        for (int x = 0; x < width; x++)

            for (int y = 0; y < height; y++)

                tileGrid[x][y].GetComponent<TileScript>().AttchTile(this);

    }

}

TileScript.cs

public class TileScript : MonoBehaviour

{

    public Dictionary<string, GameObject> connectedTiles;

    // Other properties ...

    private void Start()

    {

        connectedTiles = new Dictionary<string, GameObject>(8);

    }

    public void AttchTile (TileGridScript tileGridScript)

    {

        for (int biasx = -1; biasx < 2; biasx++)

        {

            for (int biasy = -1; biasy < 2; biasy++)

            {



                switch (biasx)

                {

                    case -1: // L

                        switch (biasy)

                        {

                            case -1: // D

                                try

                                {

                                    // !!! Catches the error here !!!

                                    connectedTiles["DL"] = tileGridScript.tileGrid[(int)position.x + biasx][(int)position.y + biasy]; 

                                }

                                catch (System.IndexOutOfRangeException) { }

                                break;

                        }

                    // etc for every Tile. P.S. DL means Down and Left.

                    // in this way I add all 8 Tiles around that

                }

            }

        }

    }

}

GameManager.cs

public class GameManager : MonoBehaviour

{

    public GameObject tileGridPrefab;

    // Other properties...

    void Start()

    {

        // !!! Here I generate the Tile Grid !!!

        tileGridPrefab.GetComponent<TileGridScript>().MakeGrid(24, 16);

    }

}

I tried to write this function in TileGrid's script and call it from that.
If I don't initialize a dictionary in Start() it does okay. Then when I access it from another script, it falls with the same error.
I tried to change the order of these scripts in the editor.

What is the reason for the problem and how can I fix it?

The problem is that Start() is calling after AttachTile().

I should use Awake() instead. I get TileGrid object in Awake() and then can use it in AttachTile() function.