NullReferenceException with boolean from other script

Question

I have 2 scripts.

script 1:

 var waarde : boolean;
 
 function Awake(){
     waarde = false;
     }

script 2:

 var waarde:boolean;
 var script1;
 
 function Awake(){
 script1 = this.gameObject.GetComponent(script1);
 waarde = script1.waarde; <-- NullReference?
 }

Answer 1

Best Answer

Answer by GuyTidhar · Jun 28, 2011 at 08:10 AM

You can not know which of the objects will be initialize first. For this reason, you should wait a frame before looking for other objects.

Do this in script 2:

  function Awake()
  {
    StartCoroutine(Initiate());
  }

  private function Initiate()
  {
     yield;
     script1 = this.gameObject.GetComponent(script1);
     waarde = script1.waarde;
  }

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Aldwoni_legacy · Jun 28, 2011 at 08:18 AM 0

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So I should do this in every script? I got this warning? BCE0043: Unexpected token: IEnumerator.

GuyTidhar · Jun 28, 2011 at 08:23 AM 0

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Oops, sorry for mixing this up - I work with C# too.

Ins$$anonymous$$d of " private IEnumerator Initiate()" do:

"private function Initiate()"

And you generally would be doing a good thing if you'd use this to avoid null reference on the get go.

I think Unity guys are going to add some management for us to be able to set the initialize order of scripts in Unity 3.5. But until then its a good idea.

Aldwoni_legacy · Jun 28, 2011 at 08:33 AM 0

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I still get the NullRefenrenceException:NullReferenceException: Object reference not set to an instance of an object Boo.Lang.Runtime.RuntimeServices.Dispatch (System.Object target, System.String cache$$anonymous$$eyName, System.Type[] cache$$anonymous$$eyTypes, System.Object[] args, Boo.Lang.Runtime.DynamicDispatching.DispatcherFactory factory) Boo.Lang.Runtime.RuntimeServices.Dispatch (System.Object target, System.String cache$$anonymous$$eyName, System.Object[] args, Boo.Lang.Runtime.DynamicDispatching.DispatcherFactory factory) Boo.Lang.Runtime.RuntimeServices.GetProperty (System.Object target, System.String name) UnityScript.Lang.UnityRuntimeServices.GetProperty (System.Object target, System.String name)

GuyTidhar · Jun 28, 2011 at 08:39 AM 0

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Do not look for components in Awake or Start. You can not know when they get initialized. Sometimes you might need script 1 to have a reference to script 2, but when you will want script 3 to have a reference to script 2, calling getcomponent in start and not awake or vise versa won't help you.

Call a coroutine with a yield from start and look for components afterwards.

Also: Is script 1 attached to the same gameObject as script 2? Cause if not it will never find it.

Aldwoni_legacy · Jun 28, 2011 at 08:56 AM 0

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thanks for your " also" ;) this works: function Awake() { StartCoroutine(Initiate()); }

private function Initiate()

{ yield; script3 = this.gameObject.GetComponent(script3); object1 = script3.object1; script2 = object1.gameObject.GetComponent(script2); waarde = script2.waarde; }

Answer 2

Answer by KeithK · Jun 28, 2011 at 08:24 AM

You should only setup references in the Awake function. Like the line below is perfect:

 script1 = this.gameObject.GetComponent(script1);

As for getting information like the value you want from that boolean. Do that in the Start function of Script 2 instead.

 function Start()
 {
     waarde = script1.waarde;
 }

This is because you cannot be sure that the Awake function of Scrip 1 is called before that of Script 2's.

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Aldwoni_legacy · Jun 28, 2011 at 08:33 AM 0

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I still get NullReferenceException: Object reference not set to an instance of an object Boo.Lang.Runtime.RuntimeServices.Dispatch (System.Object target, System.String cache$$anonymous$$eyName, System.Type[] cache$$anonymous$$eyTypes, System.Object[] args, Boo.Lang.Runtime.DynamicDispatching.DispatcherFactory factory) Boo.Lang.Runtime.RuntimeServices.Dispatch (System.Object target, System.String cache$$anonymous$$eyName, System.Object[] args, Boo.Lang.Runtime.DynamicDispatching.DispatcherFactory factory) Boo.Lang.Runtime.RuntimeServices.GetProperty (System.Object target, System.String name) UnityScript.Lang.UnityRuntimeServices.GetProperty (System.Object target, System.String name)

NullReferenceException with boolean from other script

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