Trying to spawn one object every 15 seconds (Javascript)

Unity Engine
1

Like the title says, I’m trying to make it so that every 15 seconds a new enemy will appear, to a max of 5 (plan to increase this to 80 later). However with this script:

public var enemyPrefab:GameObject;
public var enemyScripts:ArrayList = new ArrayList();

var enemyNumber = 1;
var maxEnemies = 5;

function Update()
{
	spawnEnemy();
}

function spawnEnemy()
{
	while(enemyNumber < (maxEnemies))
	{
		yield WaitForSeconds(15);
		currentEnemy = Instantiate(enemyPrefab, transform.position, transform.rotation);
		enemyNumber++;

	}
}

It waits 15 seconds, then spawns and spawns and spawns infinitely (or until I have to close Unity with the task manager), without waiting between spawns or paying any attention at all to the “maxEnemies”. I proceeded to try the relevant (at least I thought they were relevant) portions of the script here: http://www.cgauiwtalk.com/showthread.php?16136-Script-Spawning-Enemies

(“Relevant portions”)

private var enemyNumber = 1.0;
var enemyNumberMax = 10;
var enemyPrefab : GameObject;

function Update () 
{
	spawnEnemy();
}

function spawnEnemy ()
{
	while (enemyNumber <=(enemyNumberMax))
	{
		currentEnemy = Instantiate(enemyPrefab, transform.position, transform.rotation);
		enemyNumber++;
		yield new WaitForSeconds (15);
	}
}

And it pays attention to the max number (although it seems to go 1 over), however it does not wait at all, it spawns all enemies at startup. Anybody have any ideas what I’m doing wrong here?

edit: Forgot to say, I’ve tried the WaitForSeconds in the update as well, but it either A. Still gets ignored, or B. Completely negates everything in the spawn function.

2

Update runs every frame without exception and can’t be made to yield; don’t use Update unless you want something to happen literally every single frame. Making your spawn function a coroutine and then launching it from Update means you’re starting another instance of your coroutine every frame. Just use InvokeRepeating:

var enemyPrefab : GameObject;
private var enemyNumber = 1;
var maxEnemies = 5;
var spawnWaitTime = 15;

function Start () {
	InvokeRepeating ("SpawnEnemy", .01, spawnWaitTime);
}

function SpawnEnemy () {
	if (enemyNumber != maxEnemies) {
		enemyNumber++;
		currentEnemy = Instantiate(enemyPrefab, transform.position, transform.rotation);
	}
}
3

Thanks a lot, that seems to have fixed everything :slight_smile: