Question NullReferenceException but don't know why?

I'm trying to write a script that can randomly generate 'dungeons' but I have a problem where for lines 25, 31, 37, I get the error message NullReferenceException. I've added '// HERE' to where the problem is. Any help would be greatly appreciated!

Here's the script:

Code (CSharp):

1. public int openingDirection;
2.     private ComponentTemplate templates;
3.     public bool spawned = false;
4.  
5.     // Start is called before the first frame update
6.     void Start()
7.     {
8.         templates = GameObject.FindGameObjectWithTag("Components").GetComponent<ComponentTemplate>();
9.         Invoke("Spawn", 0.1f);
10.     }
11.  
12.     // Update is called once per frame
13.     void Spawn()
14.     {
15.         if (spawned == false)
16.         {
17.             if (openingDirection == 1)
18.             {
19.                 int rand = Random.Range(0, templates.bottomComponents.Length);
20.                 Instantiate(templates.bottomComponents[rand], transform.position, templates.bottomComponents[rand].transform.rotation);
21.                 Debug.Log("SpawnBottom");
22.             }
23.             else if (openingDirection == 2)
24.             {
25.                 int rand = Random.Range(0, templates.topComponents.Length); // HERE
26.                 Instantiate(templates.topComponents[rand], transform.position, templates.topComponents[rand].transform.rotation);
27.                 Debug.Log("SpawnTop");
28.             }
29.             else if (openingDirection == 3)
30.             {
31.                 int rand = Random.Range(0, templates.leftComponents.Length); // HERE
32.                 Instantiate(templates.leftComponents[rand], transform.position, templates.leftComponents[rand].transform.rotation);
33.                 Debug.Log("SpawnLeft");
34.             }
35.             else if (openingDirection == 4)
36.             {
37.                 int rand = Random.Range(0, templates.rightComponents.Length); // HERE
38.                 Instantiate(templates.rightComponents[rand], transform.position, templates.rightComponents[rand].transform.rotation);
39.                 Debug.Log("SpawnRight");
40.             }
41.             spawned = true;
42.         }
43.     }

 

Hello,
well it can't be much:
GameObject.FindGameObjectWithTag("Components") is null
or
GameObject.FindGameObjectWithTag("Components").GetComponent<ComponentTemplate>() is null
or
templates.top/left/rightComponents is null
or
Length doesn't exist in templates.top/left/right.

now it's up to you to know which one is true. I see you 'if' a lot so you're not exactly sure which 'openingDirection' is gonna work out, so checking null should be a good reflex anyway.
If templates.bottomComponents.Length is never null, then it has something to do with your declarations of top, left and right OR that openingDirection is never equal to 1

 

You have made it past step #1 below. Don't stop now!

The answer is always the same... ALWAYS. It is the single most common error ever.

Don't waste your life spinning around and round on this error. Instead, learn how to fix it fast... it's EASY!!

Some notes on how to fix a NullReferenceException error in Unity3D
- also known as: Unassigned Reference Exception
- also known as: Missing Reference Exception
- also known as: Object reference not set to an instance of an object

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.

You need to figure out HOW that variable is supposed to get its initial value. There are many ways in Unity. In order of likelihood, it might be ONE of the following:

- drag it in using the inspector
- code inside this script initializes it
- some OTHER external code initializes it
- ? something else?

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.

Here is a clean analogy of the actual underlying problem of a null reference exception:

https://forum.unity.com/threads/nul...n-instance-of-an-object.1108865/#post-7137032

 

Thanks! I figured out what it was an it was just a very simple issue. I had accidently applied the tag 'components' to the wrong game object.

 

Most NullReferenceException are Glad you could find the issue !

 

Updating the Version Control package from your project resolves the bug.
Project View -> Right-click Packages -> View in Package Manager -> Select Version Control -> Update