I want to make a Monster Spawner that spawns a monster in every x seconds (in real time); but I can't get timer to work properly...

Question

I'm trying to make a Spawner, which will Instantiate a prefab in every x seconds. I tried many times, but I can't get coroutines to work properly. This is the last form of code; which waits x seconds before spawning any prefab; after that, summons all monsters immediately. I don't know what am I missing; any help will be welcomed!
TY for taking time!

 using System.Collections;
 using UnityEngine;
 
 public class MonsterSpawner : MonoBehaviour
 {
     public GameObject[] spawnPoints;
     
     public int monstersCount;
 
     public GameObject monster2;
     private GameObject monsterSprite;
 
     public float spawnDelay = 5f;
 
     void FixedUpdate()
     {
         if (monstersCount < 1)
             Destroy(gameObject);
 
         StartCoroutine(SpawnMonster());
     }
 
     IEnumerator SpawnMonster()
     {
         yield return new WaitForSecondsRealtime(spawnDelay);
 
         int pointSelected = Random.Range(0, 3); //To use as index for reaching array of spawn points.
         Vector2 pointToSpawn = spawnPoints[pointSelected].transform.position;
 
         GameObject clonePrefab = Instantiate(monster2, pointToSpawn, Quaternion.identity);
 
         monsterSprite = clonePrefab.transform.GetChild(0).gameObject;
         if (pointSelected == 1)
             monsterSprite.GetComponent<SpriteRenderer>().flipX = true;
         else
             monsterSprite.GetComponent<SpriteRenderer>().flipX = false;
 
         monstersCount--;
     }
 }

Answer 1

The problem is you are starting a new co-routine every physics tick. I'm not sure why you are using fixed update. You could use a while statement in the coroutine and just start it once. Like so;

 using System.Collections;
 using UnityEngine;
 
 public class MonsterSpawner : MonoBehaviour
 {
     //You may as well use transform here rather than gameobjects
     public Transform[] SpawnPoints;
 
     public int MonstersCount;
 
     public GameObject Monster2;
 
     [SerializeField]
     private float _spawnDelay = 5f;
 
     private WaitForSecondsRealtime _waitTime;
 
     private void Start()
     {
         _waitTime = new WaitForSecondsRealtime(_spawnDelay);
 
         StartCoroutine(SpawnMonster());
     }
 
     IEnumerator SpawnMonster()
     {
         while (MonstersCount >= 1)
         {
             var pointSelected = Random.Range(0, 3); //To use as index for reaching array of spawn points.
             var pointToSpawn = SpawnPoints[pointSelected].position;
 
             var clonePrefab = Instantiate(Monster2, pointToSpawn, Quaternion.identity);
 
             var monsterSprite = clonePrefab.transform.GetChild(0).gameObject.GetComponent<SpriteRenderer>();
 
             if (monsterSprite != null)
             {
                 monsterSprite.flipX = pointSelected == 1;
             }
 
             MonstersCount--;
 
             yield return _waitTime;
         }
 
         Destroy(gameObject);
     }
 }

You could also use a timer in the update method and do away with the coroutine if you wish or create a method you could call to spawn x monsters whenever you wish rather than destroying the spawner.

I want to make a Monster Spawner that spawns a monster in every x seconds (in real time); but I can't get timer to work properly...

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