Instantiating prefabs with coroutine delay not working

Unity Engine
1

Greetings - Currently, I have an issue where I am attempting to instantiate a prefab multiple times, with a delay between each instantiation implemented through a coroutine. The issue is that the instantiating is happening all at once, ignoring the delays implemented in the coroutine.

This is for a simple 2D space shooter where enemy waves are being spawned. Currently, it’s attempting to spawn only one wave of 10 enemies, with a delay of 5 seconds between each enemy spawn.

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class GameManager : MonoBehaviour {
    // Object references
    [SerializeField] GameObject enemyPrefab;

    // Game parameters
    [SerializeField] float enemyStartingXPosition = 7f;
    [SerializeField] float enemyStartingYPosition = 7f;
    [SerializeField] int enemiesPerWave = 10;

    /// <summary>
    /// Start is called on the frame when a script is enabled just before
    /// any of the Update methods is called the first time.
    /// </summary>
    void Start() {
        SpawnEnemyWave();
    }

    void SpawnEnemyWave() {
        for(int i = 0; i < enemiesPerWave; i++) {
            StartCoroutine(SpawnEnemy());
        }
    }

    IEnumerator SpawnEnemy() {
        Instantiate(enemyPrefab, new Vector3(enemyStartingXPosition + Random.Range(2f, 5f), enemyStartingYPosition + Random.Range(2f, 5f), 0), Quaternion.identity);
        yield return new WaitForSeconds(5);
    }
}

If I run the above, all 10 enemies appear on my screen right at game start, whereas I was expecting each to appear after 5 seconds due to the delay in the coroutine.

Rather than a for loop, I’ve tried wrapping the Instantiate() statement in an if loop checking for a left-mouse button click in the Update function. This enables enemies to be spawned “on-demand” and works fine. It’s only when I call Instantiate() 10x in a for loop and change to a coroutine that the delay is not happening.

Any help or insights would greatly be appreciated.

2

.You are starting multiple coroutines which are all running at the same time. Put your for loop in the coroutine and start it once.

3

Perfect! Thanks for the tip, I had tried multiple things but think I misunderstood how a coroutine truly performs. I managed to fix it per your advice.