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This question was closed Jul 04, 2017 at 05:59 AM by hexagonius for the following reason:

The question is answered, right answer was accepted

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Question by Double-V · Jul 03, 2017 at 09:15 PM · c#arraynullreferenceexceptionlightarrays

Null reference exception in an if statement that checks for it.

I'm trying to make a script for a light switch and it has a bit that looks like this:

 public bool start_off = true;
 public Light light0;
 public Light light1;
 public Light light2;
 public Light light3;
 public Light light4;
 private Light[] lights;
 
 void Start ()
     {
         if (light0 != null)
         {
             lights[0] = light0;
         }
         if (light1 != null)
         {
             lights[1] = light1;
         }
         if (light2 != null)
         {
             lights[2] = light2;
         }
         if (light3 != null)
         {
             lights[3] = light3;
         }
         if (light4 != null)
         {
             lights[4] = light4;
         }
 
         //shutting lights off, if they should be off by default
         if(start_off == true)
         {
             for (int i = 0; i < lights.Length; i++)
             {
                 if(lights[i] != null)
                 {
                     lights[i].enabled = false;
                 }
             }
         }
     }
 

The line where it says lights[0] = light0 throws this error: NullReferenceException: Object reference not set to an instance of an object (wrapper stelemref) object:stelemref (object,intptr,object) SwitchLights.Start () (at Assets/Scripts/Switches/SwitchLights.cs:24)

How do I fix this? The strange part is that light0 is not empty, but assigned in inspector via drag & drop (and i'd like to retain the possibility of dragging and dropping).

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Answer by toddisarockstar · Jul 03, 2017 at 09:24 PM

you have to initialize the array and the length before you do anything with it.

  void Start (){
 lights= new Light[10] ;

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avatar image Double-V · Jul 03, 2017 at 09:25 PM 0
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But what if the length is dependent on how many of the lights will be filled in inspector?

avatar image toddisarockstar Double-V · Jul 03, 2017 at 09:29 PM 0
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you can assign any length you want to an array but they are not resizable. If you use a List ins$$anonymous$$d of an array you can resize and make it bigger while adding things along the way.

avatar image toddisarockstar toddisarockstar · Jul 03, 2017 at 09:32 PM 0
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actually looking at your code you would say:

  void Start (){
  lights= new Light[5] ;
 //now you can do stuff with it
 
avatar image Double-V · Jul 03, 2017 at 09:35 PM 0
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Allright I'll use a list then.

avatar image OusedGames · Jul 04, 2017 at 02:13 AM 2
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Why din't you JUST used the Array and fileld in the inspector, no need for many independent variables...

avatar image Bunny83 OusedGames · Jul 04, 2017 at 03:42 AM 0
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Same thought -.-

avatar image Double-V OusedGames · Jul 26, 2017 at 07:53 PM 0
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At the time I didn't know you can fill arrays in inspector, it seemed to me like it would be a too specific feature for the inspector to have.

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