How to change wait for duration SKAction ran by an SKScene?

Question

In my SpriteKit project, I have a spawnEnemy method. I want this method to be called over and over again so that enemies continue to spawn throughout the game.

What I did to achieve this is to put the spawnEnemy method in an SKAction runBlock and have my SKScene run that action forever with a delay in between calls (to prevent overloading the app).

Below is a snippet of the relevant code:

var _spawnSpeedSeconds: Double = 2.0

func startSpawning()
{
   let waitForXSeconds = SKAction.waitForDuration(self._spawnSpeedSeconds)

   let spawn = SKAction.runBlock({ () -> Void in
            self.spawnEnemy()
        })      
   self.runAction(SKAction.repeatActionForever(SKAction.sequence([spawn, waitForXSeconds])), withKey: "spawnEnemy")
}

func spawnEnemy()
{
...
}

Now after a certain time (for example when the player gets 5 points or something), I decrease the _spawnSpeedSeconds to make the enemies spawn more in a shorter amount of time to increase difficulty.

The problem is, even if I decrease my _spawnSpeedSeconds variable, the spawn action's delay being ran by the SKScene is still the same.

The only way I can think of resolving this issue is to remove the action, and then re-add the action with a new delay/spawn rate. Is there a better way to approach this issue?

Thanks

I currently code with Objective-C so i won't be able to provide a swift example. What i usually do in this situation is I create a recursive method. In this method i create a wait action and an action that runs the same method. This way you will have more control of the "delay" time and you can even have you own conditions inside Let me know if it is not clear, and if it works. — Jad Feitrouni
@JadFeitrouni Thanks for commenting. I think I get it but I just want to make sure, can you provide a snippet of code? Objective-C should be fine since I'm familiar with the language. — aresz

hamobi hamobi · Accepted Answer · 2015-02-04T22:00:12

don't use an action in this case. They don't really work in a dynamic way. Once you set them, they're stuck. just use your update method.

I'll show you how I'm periodically launching missles:

first set two timers in your class

var missleTimer:NSTimeInterval = NSTimeInterval(2)
var missleInterval:NSTimeInterval = NSTimeInterval(2)

now in our update method we count down the time and spawn missles

// subtract time from our timer
self.missleTimer -= self.delta

// when our timer reaches zero
if self.missleTimer <= 0 {
    // run your spawning code
    self.launchMissle()
    // reset timer
    self.missleTimer = self.missleInterval
}

this is better than using an action in this case because I can set missleInterval anywhere in my code and the change will always be reflected.

How to change wait for duration SKAction ran by an SKScene?

2 Answers