为什么这个 IEnumerator function 不起作用

Question

In this code I try to make a system in which before a prefab i made spawns, a particle effect appears to warn the player that the prefab will spawn there, but the prefab and particle effect don't even spawn; please help. I am new to coding so try to phrase the answers in the simplest way possible.

using System.Collections;
using System.Collections.Generic;
using System.Net.NetworkInformation;
using UnityEngine;
using System.Linq;
using System.Diagnostics;

public class EnemySpawner : MonoBehaviour
{
    public GameObject enemy;
    float randX;
    Vector2 whereToSpawn;
    public float SpawnRate = 2f;
    float nextSpawn = 0.0f;
    public GameObject marker;
   
   
  // Start is called before the first frame update
    void Start()
    {
        StartCoroutine(Thing());
    }

    // Update is called once per frame
   

    IEnumerator Thing()
    {
        if(true)
        {
            if (Time.time > nextSpawn)
            {
                nextSpawn = Time.time + SpawnRate;
                randX = Random.Range(-8.79f, 8.79f);
                whereToSpawn = new Vector2(randX, transform.position.y);
                Instantiate(marker, whereToSpawn, Quaternion.identity);
                yield return new WaitForSeconds(1);
                Destroy(marker);
                
                Instantiate(enemy, whereToSpawn, Quaternion.identity);
                
            }
        }

    }
}

Answer 1

I think you mean something like:

    while(true)
    {
        yield return new WaitForTime(SpawnRate-1);

        randX = Random.Range(-8.79f, 8.79f);
        whereToSpawn = new Vector2(randX, transform.position.y);
        Instantiate(marker, whereToSpawn, Quaternion.identity);
        yield return new WaitForSeconds(1);
        Destroy(marker);
            
        Instantiate(enemy, whereToSpawn, Quaternion.identity);   
    }