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Question by Rimbodie · Jan 02, 2014 at 11:40 PM · nullreferenceexception

NullReferenceException?

I've got a very simple script from a tutorial, but when I try to run it, it gives the NullReferenceException error in the console everytime I press one of the arrow keys.

Anyone that knows what might be wrong with my code?

Learningscript.cs: using UnityEngine; using System.Collections;

 public class LearningScript : MonoBehaviour 
 {
     GameObject capsuleGO;
     Spinner cubeComp;
     
     void start() 
     {
         capsuleGO = GameObject.Find ("Capsule");
         Debug.Log (capsuleGO);
         cubeComp = GameObject.Find ("Cube").GetComponent<Spinner>();
         Debug.Log(cubeComp);
     }
     
     void Update() 
     {
         if (Input.GetKey (KeyCode.LeftArrow)) 
         {
             capsuleGO.GetComponent<Spinner> ().SpinLeft();
         }
         
         if(Input.GetKey (KeyCode.RightArrow))
         {
             capsuleGO.GetComponent<Spinner>().SpinRight();
         }
         
         if(Input.GetKey (KeyCode.UpArrow))
         {
             cubeComp.SpinLeft();
         }
         
         if(Input.GetKey (KeyCode.DownArrow))
         {
             cubeComp.SpinRight();
         }
     }
 }

spinner.cs:

 using UnityEngine;
 using System.Collections;
 
 public class Spinner : MonoBehaviour {
 
 public void SpinLeft()
     {
         transform.Rotate (0, 0, 60 * Time.deltaTime);
     }
 
     public void SpinRight()
     {
         transform.Rotate(0, 0, -60 * Time.deltaTime);
     }
 }
 
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Answer by rutter · Jan 02, 2014 at 11:45 PM

I'll assume you understand what a NullReferenceException is. It's fine if you don't. Google might help, or just ask in a comment here.

So, you have two references: capsuleGO and cubeComp. Both are populated by a combination of GameObject.Find() and GetComponent().

  • If there is no GameObject named "Capsule", capsuleGO will be null

  • If there is no GameObject named "Cube", you'll get a null reference exception at start

  • If "Cube" exists but has no Spinner component attached, cubeComp will be null

Finally, C# is case-sensitive: start and Start are not the same name. Unity is looking for a function named Start.

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avatar image Rimbodie · Jan 03, 2014 at 11:51 AM 0
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Thanks! I triple checked the code the tutorial had written out, can't believe I missed that haha

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Answer by mohamedk2014 · Jun 11, 2019 at 04:06 PM

i have this problem this is: use capital letter in "cube" and "capsule" because the name of the game object in unity for those items begin with capital letter

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