How do i decrease time in which more enemies are created in Swift spritekit?

Question

I have a timer that spawns another enemy every second. I want it so that based on the score that the user has the time between spawning new enemies decreases. Basically, the higher the score the more thee enemies. Here is my current timer code.

    EnemyTimer = NSTimer.scheduledTimerWithTimeInterval(1.0, target: self, selector: Selector("enemies"), userInfo: nil, repeats: true)

I have tried using a var speeds = 0 and such but i get an error saying, Cannot convert value of type 'Int' to expected argument type 'NSTimeInterval' (aka 'Double'). thanks a lot — jhamer123, Oct 14 '15 at 20:31
@jhamer123 Read this http://stackoverflow.com/a/23978854/3402095 It could save you from some problems in the future. If you wonder about which problems you can run into, take a look at this : http://stackoverflow.com/q/33052867/3402095 — Whirlwind, Oct 14 '15 at 21:55

score 0 · Answer 1 · answered Oct 15 '15 at 00:45

All you need to do is make sure you use 2 or more decimal places eg: you want it to spawn faster than 1 second so..

let newSpeed = 0.75
EnemyTimer = NSTimer.scheduledTimerWithTimeInterval(newSpeed, target: self, selector: Selector("enemies"), userInfo: nil, repeats: true)

this will make them spawn every .75 seconds. Just make sure if you use whole number you do 1.0 not just 1 otherwise yes you will get the error Cannot convert value of type 'Int' to expected argument type 'NSTimeInterval' (aka 'Double')

score 0 · Answer 2 · answered Oct 15 '15 at 08:02

Instead of a timer, you can use the update function of the SKScene to spawn enemies at variable intervals. For example

var previousTime : NSTimeInterval = -1
let score = 100


func spawnEnemy() {
    print("Spawning Enemy")
}

override func update(currentTime: NSTimeInterval) {

    var spawnTimeInterval : NSTimeInterval = 1 - (NSTimeInterval(score)/1000) 

    let minSpawnTime : NSTimeInterval = 0.1

    if spawnTimeInterval < minSpawnTime {
        spawnTimeInterval = minSpawnTime
    }


    if previousTime != -1 {

        let elapsedTimeInterval = currentTime - previousTime
        if elapsedTimeInterval > spawnTimeInterval {

            spawnEnemy()
            previousTime = currentTime
        }

    } else {
        previousTime = currentTime;
    }

}

In the above code, the each 100 points will reduce 0.1 seconds from the spawnTimeInterval. You can change this calculation as per your requirements.

How do i decrease time in which more enemies are created in Swift spritekit?

2 Answers2