How to solve NullRefrenceException error and some warnings in below code ?

Questions & Answers
1

using UnityEngine;
using System.Collections;

[RequireComponent (typeof (BoxCollider2D))]
public class Controller2D : MonoBehaviour {

const float skinWidth = .015f;
public int horizontalRayCount = 4;
public int verticalRayCount = 4;

float horizontalRaySpacing;
float verticalRaySpacing;

BoxCollider2D collider;

RaycastOrigins raycastOrigins;

void start()
{
	collider = GetComponent<BoxCollider2D>();

}

void Update()
{
	UpdateRaycastOrigins ();
	calculateRayspacing (); 

	for (int i = 0; i < verticalRayCount; i++) {
		Debug.DrawRay (raycastOrigins.bottomLeft + Vector2.right * verticalRaySpacing * i, Vector2.up * -2, Color.red);
	}
}

void UpdateRaycastOrigins()
{

		
		Bounds bounds = collider.bounds;       // **error Line 38**
		bounds.Expand(skinWidth * -2);
		

		raycastOrigins.bottomLeft = new Vector2 (bounds.min.x, bounds.min.y);
		raycastOrigins.bottomRight = new Vector2 (bounds.max.x, bounds.min.y);
		raycastOrigins.topLeft = new Vector2 (bounds.min.x, bounds.max.y);
		raycastOrigins.topRight = new Vector2 (bounds.max.x, bounds.max.y);

}

void calculateRayspacing()
{

		Bounds bounds = collider.bounds;
		bounds.Expand (skinWidth * -2);

		horizontalRayCount = Mathf.Clamp (horizontalRayCount, 2, int.MaxValue);
		verticalRayCount = Mathf.Clamp (verticalRayCount, 2, int.MaxValue);

		horizontalRaySpacing = bounds.size.y / (horizontalRayCount - 1);
		verticalRaySpacing = bounds.size.x / (verticalRayCount - 1);

}

struct RaycastOrigins
{
	public Vector2 topLeft, topRight;
	public Vector2 bottomLeft, bottomRight;
}

}
…
error is:

  1. NullReferenceException: Object reference not set to an instance of an object
    Controller2D.UpdateRaycastOrigins () (at Assets/Scripts_/Controller2D.cs:38)
    Controller2D.Update () (at Assets/Scripts_/Controller2D.cs:26)

And some warnings are:

  1. Assets/Scripts_/Controller2D.cs(14,23): warning CS0108: Controller2D.collider' hides inherited member UnityEngine.Component.collider’. Use the new keyword if hiding was intended

  2. Assets/Scripts_/Controller2D.cs(11,15): warning CS0414: The private field `Controller2D.horizontalRaySpacing’ is assigned but its value is never used

Please suggest the solution to solve this code.

2

make sure BoxCollider2D is attached

BoxCollider2D col;
void Start(){
col = GetComponent<BoxCollider2D>();
}
void UpdateRaycastOrigins(){
col.bounds.Expand(skinWidth * -2);
} 
void calculateRayspacing(){
col.bounds.Expand(skinWidth * -2);
}

the last error is warning not error that tell you the variable horizontalRaySpacing is not been used & of offcourse now it should be

horizontalRaySpacing =  col.bounds.size.y / (horizontalRayCount - 1);