Destroy a prefab from another class

Question

I'm simply trying to destroy a prefab from another class using a button. However my code does not work properly.

Here is the Class that makes the prefab.

 public class MapGrid : MonoBehaviour {
  
     //Transform object
     public GameObject gridObject; 
 
 
     void Start(){
         generateGrid ();
 
     }
 
     public void generateGrid(){
         
         gridObject = Instantiate (gridObject);
 
 
     }
 }

Here is the Class that is supposed to destroy the prefab.

 public class DecreaseSize : MonoBehaviour {
     //allows access to public mapgrid fuctions
     MapGrid mg = new MapGrid();
  
 public void decreaseMapSize(){

     Destroy (Instantiate(mg.gridObject));
     }
 }

Not sure what I am doing wrong. But it is probably pretty simple.

Answer 1

Answer by Chiroculon · Apr 06, 2017 at 12:38 PM

In decreaseMapSize your are instantiating a new GameObject by copying mg.gridObject and then immediately destroying it.

So to fix it, just remove that Instantiate, like so:

  public void decreaseMapSize(){
      Destroy (mg.gridObject);
      }

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Answer 2

The DecreaseSize Class Object you want to instantiate is null. You need to take reference of the class DecreaseSize before instantiating.

 using UnityEngine;
 
 public class DecreaseSize : MonoBehaviour {
 
     //allows access to public mapgrid fuctions
     public MapGrid mg;
     private void Start()
     {
         mg = FindObjectOfType<MapGrid>();
     }
 
     public void decreaseMapSize()
     {
         Destroy(Instantiate(mg.gridObject));
     }
 }

and this is not the good way of doing it. best way is to use event system for your object to destroy. Make a non-persistent Event system Class and place all events in the class as below

 using UnityEngine;
 using UnityEngine.Events;
 
 public class EventSystemSingelton : MonoBehaviour {
 
     private static EventSystemSingelton instance;
     public static EventSystemSingelton Instance
     {
         get
         {
             if (instance == null)
             {
                 instance = GameObject.FindObjectOfType<EventSystemSingelton>().GetComponent<EventSystemSingelton>();
             }
             return instance;
         }
     }
     // Event For your object to destroy.
     public UnityEvent ObjectDestroy;
 
 }

Then in your class MapGrid listen for that event and destroy on invoke(). as below

 using UnityEngine;
 
 public class MapGrid : MonoBehaviour
 {
     public GameObject gridObject;
 
     private void Start()
     {
         EventSystemSingelton.Instance.ObjectDestroy.AddListener(delegate { Destroy(gridObject); });
         generateGrid();
     }
 
     public void generateGrid()
     {
         gridObject = Instantiate(gridObject);
     }
 }

Then invoke Event on your Button Click method in DecreaseSize class.

 using UnityEngine;
 public class DecreaseSize : MonoBehaviour {
     public void decreaseMapSize()
     {
         EventSystemSingelton.Instance.ObjectDestroy.Invoke();
     }
 }

Destroy a prefab from another class

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