Using an Array to spawn a random object

Question

I am trying to spawn a random gameobject on an empty game object when i push my mouse button. I get the following error.

NullReferenceException: Object reference not set to an instance of an object (wrapper stelemref) object:stelemref (object,intptr,object) RandomPiece.Update () (at Assets/Scripts/RandomPiece.js:17)

I can't figure out what I am doing wrong. Below is my code.

var respawnPrefab : GameObject; var respawnPrefab1 : GameObject; var respawnPrefab2 : GameObject; var respawn : GameObject; var loopHandle : boolean = true;

function Start() { if (respawn==null) respawn = GameObject.FindWithTag ("Respawn"); }

function Update() { var objs : GameObject[];

objs[0] = respawnPrefab; objs[1] = respawnPrefab1; objs[2] = respawnPrefab2;

if (Input.GetKeyDown (KeyCode.Mouse0)) {
Instantiate(objs[(Random.Range(0, objs.Length))], respawn.transform.position, respawn.transform.rotation); } }

Answer 1

Best Answer

Answer by Tourist · Dec 14, 2012 at 10:27 AM

You have a null variable.

Go to the line 17 in your script (because : (at Assets/Scripts/RandomPiece.js:17)) and then check all variables before using them.

Assuming the line 17 is : Instantiate(objs[(Random.Range(0, objs.Length))], respawn.transform.position, respawn.transform.rotation);

then check 'respawnPrefab', 'respawnPrefab1', 'respawnPrefab2' and 'respawn' are not null like this :

 var iRandomIndex = Random.Range(0, objs.Length);
 if(objs[iRandomIndex] == null)
 {
 Debug.LogError("The prefab is not referenced at index " + iRandomIndex); 
 }
 else if(respawn == null)
 {
 Debug.LogError("There is no respawn gameobject in this scene.");
 }
 else
 {
 Instantiate(objs[iRandomIndex], respawn.transform.position, respawn.transform.rotation);
 }

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ic3t3a2000 · Dec 14, 2012 at 03:22 PM 0

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I think I am declaring items in the array incorrectly but I am so new to program$$anonymous$$g that I can't say where I am wrong. Line 17 is were I am trying to link items in my array to the array I named objs.

Below are lines 16-19 where I am trying to fill my array with game objects.

var objs : GameObject[];
objs[0] = respawnPrefab;
objs[1] = respawnPrefab1;
objs[2] = respawnPrefab2;

Tourist · Dec 14, 2012 at 03:47 PM 0

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Here is a documentation on how to use arrays in javascript : http://docs.unity3d.com/Documentation/ScriptReference/Array.html

Your variable objs is null. var objs = new GameObject[3];

ic3t3a2000 · Dec 15, 2012 at 02:17 AM 0

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That did the trick!!! thanks so much!

Tourist · Dec 15, 2012 at 11:38 AM 0

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don't forget to mark the answer and close the thread

Using an Array to spawn a random object

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