Q: How can I resolve my error and how to optimize this script so the game runs smooth ?

Questions & Answers
1

I want to resolve the error I have attached but I don’t know how.

Here is the script where the error takes place (This is the line in question:

Vector2 direction = (Vector2)target.position - rb.position;)

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;



[RequireComponent(typeof(Rigidbody2D))]
public class HomingMissile : MonoBehaviour {



	


	public Transform target;

	public float delay ;

	public float speed = 5f;
	public float rotateSpeed = 200f;
	public GameObject ExplosionEffect;

	private Rigidbody2D rb;




	// Use this for initialization
	IEnumerator Start () {


		yield return new WaitForSeconds(delay);
		rb = GetComponent<Rigidbody2D>();

	}





	void FixedUpdate () {

		
		Vector2 direction = (Vector2)target.position - rb.position;

		direction.Normalize();

		float rotateAmount = Vector3.Cross(direction, transform.up).z;

		rb.angularVelocity = -rotateAmount * rotateSpeed;

		rb.velocity = transform.up * speed;

	                     }




	                   
	void OnTriggerEnter2D ()
	{
		
		Destroy(gameObject);
	     Instantiate(ExplosionEffect, transform.position, transform.rotation);
		
		ScoreScript.scoreValue += 1;


	}






}
3

Your error is due to the delay you set before getting the Rigidbody.

Your Start method will wait for delay amount of seconds. In the meanwhile, your FixedUpdate is running but the rigidbody reference is null.

I don’t know why you are stalling in the Start but either you don’t:

void Start() 
{
     rb = GetComponent<Rigidbody>();
}

or if you have a reason to do so, skip the FixedUpdate until the rigidbody is valid:

void FixedUpdate()
{
      if(rb == null) { return; }
}
2

@Vlad_96
I am also a beginner, so I will explain what I know
1.) don’t use Start as a coroutine it will only runs once.
use
void Start()
{
rb.GetComponent();
} move dealy to a separate coroutine
2.)I think You are getting Null reference exceptions at line 45 because you are using
“[RequireComponent(typeof(Rigidbody2D))]” incorrectly. and it is not rigidbody2d to the missile
make a prefab of the missile and attach rigidbody2d to it and use it instead
3.)use this code in update
Vector2 direction = (Vector2)(target.position - rb.position);
direction.Normalize(); as they require to update constantly