2D array generated with custom inspector, null when starting game?

2D arrays can't be serialized by Unity. You basically have two options:

• use a 1d array of a custom class which contains another 1d array

• use a "flattend" 1d array.

Example for the first case:

 //C#
 
 [System.Serializable]
 public class SubArray
 {
     public GameObject[] objs;
 }
 
 public class SomeScript : MonoBehaviour
 {
     public SubArray[] array;
 }

This is basically like a "jagged" array (a nested array) but it's serializable by Unity. You can access an element like this:

 GameObject o = array[dim0Index].objs[dim1Index];

The other solution is to use a flattend array. For this all you need is an additional integer variable that specifies the "width" of the 2d array:

 public int arrayWidth = 10;
 public GameObject[] array;

To access an element you just have to calculate the appropriate index manually. You can implement a get and set method for it:

 public GameObject GetElement(int xIndex, int yIndex)
 {
     int index = xIndex + yIndex * arrayWidth;
     return array[index];
 }
 
 public void GetElement(int xIndex, int yIndex, GameObject val)
 {
     int index = xIndex + yIndex * arrayWidth;
     array[index] = val;
 }

To create the array you just have to multiply your desired xSize with the ySize of the array:

 public void CreateArray(int xSize, int ySize)
 {
     array = new GameObject[xSize * ySize];
     arrayWidth = xSize;
 }

The 1D array can be serialized by Unity.