Help on my 2D space shooter game (shooting the laser)

Hey there,

First I want to apologize, as I am new to Unity and new to C# coding. For anyone willing to help this newb, I greatly appreciate it!

So, so far, I've got the ship moving and many facets working the way they should: The rigidbody, movement, damage, box collider, etc... I even have the laser shooting. However, it automatically shoots at the beginning (not supposed to happen), then it is destroyed (as it is supposed to) once it is off the screen. I can shoot the laser as many times as I want... UNTIL the first laser is destroyed, then it glitches and ends the game, giving me an error:

"MissingReferenceException: The object of type 'GameObject' has been destroyed but you are still trying to access it.
Your script should either check if it is null or you should not destroy the object."

Having said that (and not knowing where the problem is) I will post the C# code I wrote for the Laser, as well as the SelfDestruct, WeaponMovement, and Damage. And again, I greatly appreciate anyone that is able to help. Let me know if I'm missing anything, or anything you may need in order to help me out.

To sum up:

1) I need help to get the laser to stop shooting on its own at the beginning.
2) I need to destroy the laser once off screen; however, I need the ability to continue shooting the laser at any time (for obvious reasons...)


Laser:

Code (CSharp):

1. using UnityEngine;
2. using System.Collections;
3.  
4. public class Laser : MonoBehaviour
5. {
6.  
7.     public Vector3 bulletOffset = new Vector3(0, 0.5f, 0);
8.  
9.     public GameObject bulletPrefab;
10.     int bulletLayer;
11.  
12.     public float fireDelay = 0.5f;
13.     float cooldownTimer = 0;
14.  
15.     void Start()
16.     {
17.         bulletLayer = gameObject.layer;
18.     }
19.  
20.     // Update is called once per frame
21.     void Update()
22.     {
23.         cooldownTimer -= Time.deltaTime;
24.  
25.         if (Input.GetButton("Laser") && cooldownTimer <= 0)
26.         {
27.             // SHOOT!
28.             cooldownTimer = fireDelay;
29.  
30.             Vector3 offset = transform.rotation * bulletOffset;
31.  
32.             GameObject bulletGO = (GameObject)Instantiate(bulletPrefab, transform.position + offset, transform.rotation);
33.             bulletGO.layer = bulletLayer;
34.  
35.         }
36.  
37.     }
38. }

SelfDestruct:

Code (CSharp):

1. using UnityEngine;
2. using System.Collections;
3.  
4. public class SelfDestruct : MonoBehaviour
5. {
6.  
7.     public float timer = 3f;
8.  
9.     void Update()
10.     {
11.         timer -= Time.deltaTime;
12.  
13.         if (timer <= 0)
14.         {
15.             Destroy(gameObject);
16.         }
17.     }
18. }

WeaponMovement:

Code (CSharp):

1. using UnityEngine;
2. using System.Collections;
3.  
4. public class weaponmovement : MonoBehaviour
5. {
6.  
7.     public float maxSpeed = 5f;
8.  
9.     // Update is called once per frame
10.     void Update()
11.     {
12.         Vector3 pos = transform.position;
13.  
14.         Vector3 velocity = new Vector3(0, maxSpeed * Time.deltaTime, 0);
15.  
16.         pos += transform.rotation * velocity;
17.  
18.         transform.position = pos;
19.     }
20. }

Damage:

Code (CSharp):

1. using UnityEngine;
2. using System.Collections;
3.  
4. public class damage : MonoBehaviour
5. {
6.  
7.     public int health = 1;
8.  
9.     public float invulnPeriod = 0;
10.     float invulnTimer = 0;
11.     int correctLayer;
12.  
13.     SpriteRenderer spriteRend;
14.  
15.     void Start()
16.     {
17.         correctLayer = gameObject.layer;
18.  
19.         // NOTE!  This only get the renderer on the parent object.
20.         // In other words, it doesn't work for children. I.E. "enemy01"
21.         spriteRend = GetComponent<SpriteRenderer>();
22.  
23.         if (spriteRend == null)
24.         {
25.             spriteRend = transform.GetComponentInChildren<SpriteRenderer>();
26.  
27.             if (spriteRend == null)
28.             {
29.                 Debug.LogError("Object '" + gameObject.name + "' has no sprite renderer.");
30.             }
31.         }
32.     }
33.  
34.     void OnTriggerEnter2D()
35.     {
36.         health--;
37.  
38.         if (invulnPeriod > 0)
39.         {
40.             invulnTimer = invulnPeriod;
41.             gameObject.layer = 10;
42.         }
43.     }
44.  
45.     void Update()
46.     {
47.  
48.         if (invulnTimer > 0)
49.         {
50.             invulnTimer -= Time.deltaTime;
51.  
52.             if (invulnTimer <= 0)
53.             {
54.                 gameObject.layer = correctLayer;
55.                 if (spriteRend != null)
56.                 {
57.                     spriteRend.enabled = true;
58.                 }
59.             }
60.             else
61.             {
62.                 if (spriteRend != null)
63.                 {
64.                     spriteRend.enabled = !spriteRend.enabled;
65.                 }
66.             }
67.         }
68.  
69.         if (health <= 0)
70.         {
71.             Die();
72.         }
73.     }
74.  
75.     void Die()
76.     {
77.         Destroy(gameObject);
78.     }
79.  
80. }

 

Some notes on how to fix a NullReferenceException error in Unity3D
- also known as: Unassigned Reference Exception
- also known as: Missing Reference Exception

http://plbm.com/?p=221

The basic steps outlined above are:
- Identify what is null
- Identify why it is null
- Fix that.

Expect to see this error a LOT. It's easily the most common thing to do when working. Learn how to fix it rapidly. It's easy. See the above link for more tips.

This is the kind of mindset and thinking process you need to bring to this problem:

https://forum.unity.com/threads/why-do-my-music-ignore-the-sliders.993849/#post-6453695

Step by step, break it down, find the problem.

 

Gather the value

Input.GetButton("Laser")

to a temporary boolean and use Debug.Log() to print it out. It must be true when you don't think it is, or else something else is making your bullet.

 

One way is to put an object just barely off the top of the screen and give the bullet a reference to that object. If the bullet's position ever goes north of that object, Destroy() it.

 

Code (CSharp):

1.  void Update()
2.     {
3.         timer -= Time.deltaTime;
4.         if (timer <= 0)
5.         {
6.             Destroy(gameObject);
7.         }
8.     }

After destroying gameObject once. You are destroying it many more times. You need to stop destroying the gameObject if it does not exist.