NullReferenceException help (416101)

Unity Engine
1

Hi, I’m having problems with a NullReferenceException. I can’t figure out what the problem is. Here’s the details:

I’m getting the exception for the first
wheels[0].wheelGraphic = FLWheel;
and if I comment it out the exception moves to the next one.

var FLWheelCollider : WheelCollider;
var FRWheelCollider : WheelCollider;
var RLWheelCollider : WheelCollider;
var RRWheelCollider : WheelCollider;

var FLWheel : Transform;
var FRWheel : Transform;
var RLWheel : Transform;
var RRWheel : Transform;

private var wheels : WheelData[];

class WheelData
{
	var collider : WheelCollider;
	var wheelGraphic : Transform;
	var poweredWheel : boolean = false;
	var steerWheel : boolean = false;
	var lastSkidmark : int = -1;
	var lastEmitPosition : Vector3 = Vector3.zero;
	var lastEmitTime : float = Time.time;
	var wheelVelo : Vector3 = Vector3.zero;
	var groundSpeed : Vector3 = Vector3.zero;
}

function Start()
{
	rigidbody.centerOfMass = centerOfMass.localPosition;
	
	SetupWheelColliders();
}




function SetupWheelColliders()
{			
	wheels = new WheelData[4];
	
	wheels[0].wheelGraphic = FLWheel;
	wheels[0].collider = FLWheelCollider;
	wheels[1].wheelGraphic = FRWheel;		
	wheels[1].collider = FRWheelCollider;
	wheels[2].wheelGraphic = RLWheel;
	wheels[2].collider = RLWheelCollider;
	wheels[3].wheelGraphic = RRWheel;	
	wheels[3].collider = RRWheelCollider;
}

And heres the image of the attached Colliders and Transforms.

328912--11590--$capture_901.jpg
328912--11590--$capture_901.jpg361×193 19.1 KB

2

Straightforward fix, you are just a step shy of having everything initialized properly. This statement creates an empty WheelData array of length 4:

wheels = new WheelData[4];

What you need to do here is create an instance of WheelData for each wheel and then set those object references within the array:

wheels[0] = new WheelData();

Now wheels[0] is now pointing at a non-null object and you can proceed with the property setters.

3

awesome, thanks very much