Preventing my game object from multiplying due to DontDestroyOnLoad()

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I've been trying to implement a game object that is created at the "mainmenu" scene of my game that is intended to be omnipresent. This would allow me to easily manage things such as save data, user inventory, and state management all within one or multiple classes.

Currently, I have the Game_Manager class extending from MonoBehavior which runs the DontDestroyOnLoad() function inside it's Start() function. This works well and the Game_Manager game object exists even upon scene transitions (currently to a test scene), yet the current set up allows the game object to multiply itself as it is re-created upon loading the original main menu scene. In other words, whenever I switch back to the main menu level it will create another Game_Manager object.

One solution for this would be to make a "Initialize" scene which only has the function of introducing omnipresent game objects and will never be loaded again during runtime, but this solution seems less than ideal. Is there any way to prevent the game object from creating itself if one of a similar name already exists using a simple unity function / parameter or should I instead rely on creating a singleton gameobject? Feel free to throw in any other suggestions. I'm using C# for all scripting / programming in unity thus far.

Answer 1

Best Answer

Answer by whydoidoit · Oct 09, 2012 at 06:51 AM

Use a static variable to work out whether the object has already been loaded - destroy any copies if the static is set.

  public class MyPersistentThing : MonoBehaviour
 {
       public static MyPersistentThing Instance;
 
       void Awake()
       {
             If(Instance)
                 DestroyImmediate(gameObject);
             else
             {
                 DontDestroyOnLoad(gameObject);
                 Instance = this;
             }
       }
 }

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TheYokai · Oct 09, 2012 at 07:04 AM 0

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Thanks, this seems to work.

Kerihobo · Dec 04, 2014 at 12:00 AM 0

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how did you get this to work?

I don't understand what this line is doing:

 public static $$anonymous$$yPersistentThing Instance;

none of those keywords are a "type"?

Is "$$anonymous$$yPersistentThing" the variable name? or is "Instance" the variable name? Assu$$anonymous$$g "Instance" is the variable name... what is "$$anonymous$$yPersistentThing"? GameObject?

mr_freedo Kerihobo · Sep 14, 2015 at 08:28 AM 1

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Change out $$anonymous$$yPersistentThing with the name of the class, and dont make a new class. $$anonymous$$y class is called Options$$anonymous$$enuScript so for me the code looks like this:

 public static Options$$anonymous$$enuScript Instance;
     
     void Awake()
     {
         if(Instance){
             DestroyImmediate(gameObject);
         }else
         {
             DontDestroyOnLoad(gameObject);
             Instance = this;
         }
     }

This worked for me so it should work for you as well, know its a long time since you posted, so this is most for other people having the same question.

RudyTheDev · Dec 04, 2014 at 12:26 AM 0

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$$anonymous$$yPersistentThing is the type, in this case it's a class ( public class $$anonymous$$yPersistentThing : $$anonymous$$onoBehaviour ). Instance is the variable/identifier name.

mr_freedo · Sep 14, 2015 at 08:23 AM 0

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Thanks a lot, This was realy helpful

Answer 2

Answer by BillyBobBeavis · Mar 07, 2021 at 11:52 PM

My solution, which is more straightforward for numskulls like me, was to attach this script to any persistent GameObject. Seems to work. . . so far. This script should work unmodified with any GameObject that has a tag.

 public class DestroyDuplicateOnLoad : MonoBehaviour
 {
     private void Awake()
     {
         var otherPersistent = GameObject.FindWithTag(gameObject.tag);
         if (otherPersistent != null && otherPersistent != transform.gameObject)
             DestroyImmediate(transform.gameObject);
     }
 }

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Preventing my game object from multiplying due to DontDestroyOnLoad()

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