Getting "Object reference not set to an instance of an object" Error

Question

         var ballArray : Array;
         ballArray = GameObject.FindGameObjectsWithTag("PunishmentBall");
         ballArray.Add(GameObject.FindGameObjectsWithTag("StandardBall"));
         ballArray.Add(GameObject.FindGameObjectsWithTag("PowerUpBall"));
 
         var balls : GameObject[] = new GameObject[ballArray.length];
 
         for(var i = 0; i < ballArray.length; i++)
         {
             (ballArray[i] as GameObject).GetComponent(BallController).startSlow = Time.time;
             (ballArray[i] as GameObject).GetComponent(BallController).isSlowed= true;
         }

I have a trigger object that reads what it collides with, then performs an action. The code is supposed to get all the balls on the screen, then slow them down, but I get

NullReferenceException: Object reference not set to an instance of an object

Whenever it collides with this ball. The error occurs at line 8 here,

(ballArray[i] as GameObject).GetComponent(BallController).startSlow = Time.time;

Answer 1

Answer by hvilela · Oct 06, 2012 at 07:31 PM

Do you have objects with "StandardBall" and "PowerUpBall" tags? Cause if you don't, it'll return null and add a null reference to your array. Be aware that TAG is not NAME. To find object by name you should use just "Find".

Also, are you sure that your objects have the BallController component?

Anyway, I recommend you to add a Debug to your code to check if all the entries in your array are valid:

 var ballArray : Array;
 ballArray = GameObject.FindGameObjectsWithTag("PunishmentBall");
 ballArray.Add(GameObject.FindGameObjectsWithTag("StandardBall"));
 ballArray.Add(GameObject.FindGameObjectsWithTag("PowerUpBall"));

 for(var i = 0; i < ballArray.length; i++)
 {
     if (ballArray[i] != null) {
         var ballController = (ballArray[i] as GameObject).GetComponent(BallController);

         if (ballController != null) {
             ballController.startSlow = Time.time;
             ballController.GetComponent(BallController).isSlowed= true;
         } else {
             Debug.Log(i + " has no ball controller");
         }
     } else {
         Debug.Log(i + " is null!");
     }
 }

PS: Your "balls" variable is doing nothing.

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Zacharias3690 · Oct 06, 2012 at 09:24 PM 0

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Thanks, the balls variable was a different attempt, didn't realize I forgot to delete it. I put your code in, and I'm still getting the same error when you fetch the ballcontroller, but I check my prefabs, and all of the have the script attached.

hvilela · Oct 06, 2012 at 10:02 PM 0

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The objective of my code is not to solve the problem, but to identify it. Run it an look at the console output (Window -> Console).

Zacharias3690 · Oct 07, 2012 at 03:30 AM 0

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I did, that's what I meant, I get the error, no debug code

Getting "Object reference not set to an instance of an object" Error

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