Resolved How to set references to instantiated instances?

My goal is something like this. On character entering a trigger box,text comes up, and when the user presses E, something will happen. But the player is required to have a prefab in their "hands" to allow that to happen when they enter the trigger.

Because the prefab is instantiated i set it to an instance

Code (CSharp):

1.     private void Update()
2.     {
3.         if (newChainCanvas.enabled)
4.         {
5.             if (Input.GetKeyDown(KeyCode.E))
6.             {
7.                 newChainInstance = Instantiate(newChainPrefab, hand.position, Quaternion.identity);
8.                 newChainInstance.transform.parent = hand;
9.                 return;
10.             }
11.         }
12.     }

where newChainInstance is a static Serialized field.

Then, in a seperate script attached the to trigger box, I'm checking if the prefab's transform is equal to the "hand"'s transform. So, the player is holding the object.

Code (CSharp):

1.     private void OnTriggerEnter(Collider other)
2.     {
3.         if (other.CompareTag("Player"))
4.         {
5.             Debug.Log("Player enetered trigger");
6.             if (hand.position == newChainInstance.transform.position)//minigame finishedin chain fix script
7.             {
8.                 Debug.Log("is holding");
9.             {
10.          {
11.      {
12.  
13.  

My player is detected enetering the trigger box. But an error occurs on line 6 "NullReferenceException: Object reference not set to an instance of an object".
I'm guessing that when newChainInstance was set in the first script, it ran under multiple conditions in the update function, so the other script cannot detect newChainInstance because they are running at the same time?? But I'm confused about that because it's updating every frame. I tried using return, but I don't think it actually does anything because Update is called every frame anyways.
This suspicion is probabaly incorrect, but is there a reason that the reference isn't detected?

 

Don't guess, debug!

The answer is always the same... ALWAYS!

How to fix a NullReferenceException error

https://forum.unity.com/threads/how-to-fix-a-nullreferenceexception-error.1230297/

Three steps to success:
- Identify what is null <-- any other action taken before this step is WASTED TIME
- Identify why it is null
- Fix that

ALSO: this is extremely unlikely to work:

Use a distance check instead.

Here's why:

Floating (float) point imprecision:

Never test floating point (float) quantities for equality / inequality. Here's why:

https://starmanta.gitbooks.io/unitytipsredux/content/floating-point.html

https://forum.unity.com/threads/debug-log-2000-0f-000-1f-is-200.1153397/#post-7399994

https://forum.unity.com/threads/why-doesnt-this-code-work.1120498/#post-7208431

"Think of [floating point] as JPEG of numbers." - orionsyndrome on the Unity3D Forums

 

The trigger is checking the player's hand the moment they enter the trigger and is finding that newChainInstance hasn't been set. The player then presses E and sets newChainInstance but it's too late, the moment has passed, the trigger is no longer checking.

OnTriggerEnter only happens once the moment an object enters and doesn't happen again until the object leaves and renters. Or if another object enters.

You need OnTriggerStay:

Code (CSharp):

1.     private void OnTriggerStay(Collider other)
2.     {
3.         if (other.CompareTag("Player"))
4.         {
5.             Debug.Log("Player enetered trigger");
6.             if (newChainInstance)
7.             {
8.                 Debug.Log("is holding");
9.             }
10.         }
11.     }