Why can't GameObject.Find find more than one object at the start function?

Question

Okay so i'm setting up this real quick 2d game where you can only move left and right and catch objects falling from the top of the screen. i decided to add 3 hearts at the top right side of the screen and everytime you miss an object one heart dissapears. In the "Spawnables" Script applied to all the different prefabs that fall from the sky, i declared a float variable called objectsMissed, now everytime an object reaches -6 on the y axis it will be destroyed since it's not on the screen anymore and we add 1 to the objectsMissed variable. The problem is these objects are prefabs and you cannot assign gameObjects to prefabs so i have to find them through script at the start function, the first heat(furthest right) dissapears when i first miss an object, but when i miss a second it gives me this error(NullReferenceException: Object reference not set to an instance of an object). Here's my code.

 public float objectsMissed;
 
     private GameObject heart1;
     private GameObject heart2;
     private GameObject heart3;
 
     void Start()
     {
         objectsMissed = 0;
         
         heart1 = GameObject.Find("HeartR");
         heart2 = GameObject.Find("HeartM");
         heart3 = GameObject.Find("HeartL");


      void Update()
     {
         if (transform.position.y <= yBounds)
         {
             Destroy(gameObject);
             objectsMissed++;
         }
 
         if (objectsMissed == 1)
         {
             heart1.SetActive(false);
         }
         else if(objectsMissed == 2)
         {
             heart2.SetActive(false);
         }
     }

Answer 1

Having the falling objects handle the hearts is not the way to go.

You need to rework the architecture of your game. Suggested architecture:

CODE NOT TESTED

1. A Life script, placed in your scene, handling the hearts

 public class Life : MonoBehaviour
 {
      // Drag & drop the hearts in the inspector
      [SerializeField] private GameObject[] hearts;
 
      private int amount;
 
      public int Amount => amount;
 
      private void Awake()
      {
          amount = hearts.Length;
      }
 
      public void Decrease()
      {
           if(amount == 0) return;
 
           hearts[amount - 1].SetActive(false);
           amount--;
      }
 }

2. A Spawner script, placed in your scene, handling the spawn of your objects. You should already have something similar

 public class Spawner : MonoBehaviour
 {
      // Drag & drop in the inspector the prefab to spawn, replace `Spawnee` by the name of your script
      [SerializeField] private Spawnee prefab;
 
      // Drag & drop the object with the Life component in the inspector
      [SerializeField] private Life life;
 
      private IEnumerator spawnCoroutine;
 
      private void Start()
      {
          spawnCoroutine = Spawn();
          StartCoroutine(spawnCoroutine);
      }
 
      private IEnumerator Spawn()
      {
          WaitForSeconds wait = new WaitForSeconds(5);
          while(true)
          {
               yield return wait;

               // Consider using a pool instead of destroying and instantiating
               Spawnee spawnee = Instantiate(prefab);
               spawnee.Despawned += OnSpawneeDespawned;
          }
      }
 
      private void OnSpawneeDespawned(Spawnee spawnee)
      {
          spawnee.Despawned -= OnSpawneeDespawned;
          life.Decrease();
          if(life.Amount == 0)
              StopCoroutine(spawnCoroutine);
      }
 }

3. A Spawnee script, placed on your prefab you instantiate. Basically the script you have in your question

 public class Spawnee : MonoBehaviour
 {
      [SerializeField] private float yBounds;
 
      public event System.Action<Spawnee> Despawned;
 
      void Update()
      {
          if (transform.position.y <= yBounds)
          {
              Despawned?.Invoke(this);
              Destroy(gameObject);
          }
      }
 }

Why can't GameObject.Find find more than one object at the start function?

1 Reply

CODE NOT TESTED

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