Strange Unity Code Problem

Unity Engine
1

Hey all i’ve written a basic script and it keeps giving me this error.

NullReferenceException: Object reference not set to an instance of an object
scrGUI.CreateGrid () (at Assets/[Scripts]/Player - Scripts/scrGUI.js:41)
scrGUI.Main () (at Assets/[Scripts]/Player - Scripts/scrGUI.js:26)

I will outline the important parts

Where the error is:

var grid : InvGrid[];
grid = new InvGrid[totalSlots];

CreateGrid();


function CreateGrid()
{
	var slotW = 50;		
	var slotH = 50;
	var startX = (-4 * slotW);
	var startY = screenH + 230;
	
	for(var i=0;i<1;i++)
	{

	print("Commencing");
		
		grid[0].minX = screenW + startX + (i*slotW);
		grid[0].maxX = screenW + startX + (i*slotW) + slotW;
		grid[0].minY = startY;
		grid[0].maxY = startY - 50;

	print("Done");
	}

}

The class is outlined at the bottom of the script

class InvGrid
{
	var minX = 0;
	var maxX = 0;
	
	var minY = 0;
	var maxY = 0;
}

I see no reason for it not to work… I have used the same layout in other scripts. Is it just unity?

Any help is really appreciated, Thanks

2

You’ve told grid that it will be holding InvGrid classes, but you’re trying to alter something that isn’t there yet.

print("Commencing");

grid[0] = new InvGrid ();  // Added this line

grid[0].minX = screenW + startX + (i*slotW);
grid[0].maxX = screenW + startX + (i*slotW) + slotW;
grid[0].minY = startY;
grid[0].maxY = startY - 50;

print("Done");

By the way, I think you mean ‘i’ not ‘0’ in the array index.

3

I do mean i, 0 was just for testing purposes.

grid was set above that code, does that affect it?

P.S same error anyway

4

Is that your exact code? You shouldn’t be calling functions out there!

Place your call to CreateGrid inside of Start or Awake.

5

My complete code US

//Mouse Vector2  Screen
var mouseVec : Vector2;
var screenH : int;
var screenW : int;
screenH = Screen.height/2;
screenW = Screen.width/2;

//Parent Variables
var invScript : scriptPlayer;
invScript = transform.parent.GetComponent(scriptPlayer);

//Inventory Variable
var invOpen = false;
var totalSlots : int; totalSlots = invScript.invSlots;
var hotbarLen : int;




CreateGrid();


function CreateGrid()
{
	var slotW = 50;		
	var slotH = 50;
	var startX = (-4 * slotW);
	var startY = screenH + 230;
	
	var grid : InvGrid[];
	grid = new InvGrid[totalSlots];
	
	for(var i=0;i<1;i++)
	{

	print("Commencing");
			
		grid[i].minX = screenW + startX + (i*slotW);
		grid[i].maxX = screenW + startX + (i*slotW) + slotW;
		grid[i].minY = startY;
		grid[i].maxY = startY - 50;

	print("Done");
	}

}


////////////////////////////////////////////
//Update
////////////////////////////////////////////

function Update()
{
mouseVec = Vector2(Input.mousePosition.x,Input.mousePosition.y);
screenH = Screen.height/2;
screenW = Screen.width/2;
}

////////////////////////////////////////////
//Inv Grid Class
////////////////////////////////////////////

class InvGrid
{
	var minX = 0;
	var maxX = 0;
	
	var minY = 0;
	var maxY = 0;
}

Should work right?

P.S Going to try on a different computer, to eliminate that posibility

6

No, do as I suggested.

// instead of the call on line 20

function Start () {
    CreateGrid ();
}
7

Nope same error

8

Let me guess, you took out the

grid[0] = new InvGrid ();  // Added this line

It is still needed.

EDIT: Looking at your code, why did you move

var grid : InvGrid[];

grid = new InvGrid[totalSlots];

inside the function? You won’t be able to access it from anywhere else now.

9

1.Nope. Did not take that out.

2.Changed that after I posted it

10

That’s odd, I took the code in your OP, placed CreateGrid inside Start and created an InvGrid instance at index 0 and it worked fine for me.

11

Wow.

That was extremely stupid of me i should have known better… There was nothing defining grid like you said.

THANK YOU THANK YOU THANK YOU

You’ve been a great help

Result Code:

var grid : InvGrid[];
grid = new InvGrid[totalSlots];


CreateGrid();

////////////////////////////////////////////
//Create Grid
////////////////////////////////////////////

function CreateGrid()
{
	var slotW = 50;		
	var slotH = 50;
	var startX = (-4 * slotW);
	var startY = screenH + 230;
	
	
	for(var i=0;i<8;i++)
	{

	print("Commencing");
	grid[i] = new InvGrid();
	
		grid[i].minX = screenW + startX + (i*slotW);
		grid[i].maxX = screenW + startX + (i*slotW) + slotW;
		grid[i].minY = startY;
		grid[i].maxY = startY - 50;

	print("Done");
	}

}