Question Trying to access a class outside of file but getting Object reference error

Hello,
I'm trying create a global class that I can access and modify from outside of the script but I keep getting this error:

Code (CSharp):

1. NullReferenceException: Object reference not set to an instance of an object
2. GridSystem.Start () (at Assets/Scripts/Grid/GridSystem.cs:45)

Here's the code of the class:

Code (CSharp):

1. using System.Collections;
2.     using System.Collections.Generic;
3.     using UnityEngine;
4.  
5.     [System.Serializable]
6.     public class GridManager : MonoBehaviour
7.     {
8.         private static GridManager _gridManager;
9.         public static GridManager Instance { get { return _gridManager; } }
10.         void Awake()
11.         {
12.             _gridManager = this;
13.         }
14.  
15.         public GridSlot[] allGrids = new GridSlot[10100];
16.  
17.         public void AddGridSlot(int id, Vector3 pos)
18.         {
19.             allGrids[id]            = new GridSlot();
20.             allGrids[id].id         = id;
21.             allGrids[id].position   = pos;
22.             allGrids[id].leftSlot   = id - 1;
23.             allGrids[id].rightSlot  = id + 1;
24.             allGrids[id].aboveSlot  = id + 100;
25.             allGrids[id].leftSlot   = id - 100;
26.             allGrids[id].beingUsed  = false;
27.         }
28.     }

And here's the code where I'm trying to use the class instance outside of the file:

Code (CSharp):

1.   GridManager.Instance.AddGridSlot(i, new Vector3(curX, max.y, curZ));

Thanks for the help

 

Assuming

GridManager.Instance.AddGridSlot(i, new Vector3(curX, max.y, curZ));

is line 45 of GridSystem.cs then it stands to reason you simply don't have a GridManager in your scene.

 

I don't know why I thought I didn't have to actually add it to the scene. That fixed it.

Thanks