On Collision Enter Object Variable Acces NullReferenceException

Question

I'm trying to access the stats of an opponent, but there is a nullreferenceexception for the lines defining optype1 and optype2

     function OnCollisionEnter(collision:Collision)

{

 print("hi");

 var optype1 = collision.gameObject.GetComponent(BaseStats).type1;

 var optype2 = collision.gameObject.GetComponent(BaseStats).type2;

How should I fix it?

Answer 1

Answer by aldonaletto · Sep 29, 2011 at 04:10 AM

You may be having collisions with the ground or other objects that don't have the script BaseStats. The easiest way to avoid this is to check if the object hit has a BaseStats script:

function OnCollisionEnter(collision:Collision) 
{
  var baseStScript: BaseStats = collision.gameObject.GetComponent(BaseStats);
  if (baseStScript){
    var optype1 = baseStScript.type1;
    var optype2 = baseStScript.type2;
    ...
  }
}

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Bob1 · Sep 29, 2011 at 04:47 PM 0

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I've tried it and it helps, but there is another error in the last line of the following:

var baseStScript: BaseStats = collision.gameObject.GetComponent(BaseStats);

   if (baseStScript)

 {

 print("hi");

 var optype1 = baseStScript.type1;

 var optype2 = baseStScript.type2;

 var STAB = shooter.GetComponent(BaseStats).type1;

 var STAB2 = shooter.GetComponent(BaseStats).type2;



 if(movestyle==0)

 {    

     def = baseStScript.defense;

     atk = shooter.GetComponent(BaseStats).attack;

 }

 if(movestyle==1)

 {

     def = baseStScript.specialdefense;

     atk = shooter.GetComponent(BaseStats).specialattack;

 }





 damage = $$anonymous$$athf.RoundToInt(((((2*shooter.level/5+2)*atk*basepower/def)/50)+2)*STAB*STAB2*(Random.Range(85,100)/100));

It's saying that: NullReferenceException: Object reference not set to an instance of an object Boo.Lang.Runtime.RuntimeServices.InvokeBinaryOperator (System.String operatorName, System.Object lhs, System.Object rhs) DamageScript.OnCollisionEnter (UnityEngine.Collision collision) (at Assets/Standard Assets/Reusable Scripts/ New Scripts/Generic/DamageScript.js:36)

aldonaletto · Sep 29, 2011 at 07:02 PM 0

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Which line is 36? The last one? In the last line you have shooter.level, which doesn't seem to make much sense: from the other lines, shooter seems to be a Transform of GameObject, and none of them have a level property. Could it be a BaseStats variable? By the way, it would be better to save at the beginning a reference to the shooter BaseStats script, like we did with the variable baseStScript:

var shooterScript: BaseStats = shooter.GetComponent(BaseStats);
var STAB = shooterScript.type1;
var STAB2 = shooterScript.type2;
...

Bob1 · Sep 29, 2011 at 09:11 PM 0

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shooter is a transform/gameobject variable that yet another script acesses and sets. It's not assigned by BaseStats.

A move script on the shooter does this:

instanceball.GetComponent(DamageScript).shooter = transform;

then the bullet has the damage script with the variable shooter

On Collision Enter Object Variable Acces NullReferenceException

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