patrickd patrickd - 6 months ago 24
Swift Question

swift spritekit increase frequency of node creation as time goes on

I have figured out how to continuously spawn a node every x seconds. However, I would like to decrease the time that I wait to create a node as the game goes on, to increase the difficulty. For example, I call this function in didMoveToView:

func createSequentialEnemies(){

This creates an enemy every 2 seconds, but I want to decrease this duration arbitrarily. For example, say that after 30 seconds of gameplay I want to now spawn enemies every 1.5 seconds. How would I change the duration dynamically?


Create a spawnDuration property and key reference in your scene class.

class SomeClass: SKScene {

       private var spawnDuration: NSTimeInterval = 2.0
       private let spawnKey = "SpawnKey"


Than adjust your spawn code to use this key. I slightly changed the syntax as well to make it more legible in my opinion.

func createSequentialEnemies(){
      removeActionForKey(spawnKey) // remove previous action if running. This way you can adjust the spawn duration property and call this method again and it will cancel previous action.

      let spawnAction = SKAction.runBlock(createEnemy)
      let spawnDelay = SKAction.waitForDuration(spawnDuration)
      let spawnSequence = SKAction.sequence([spawnAction, spawnDelay])
      runAction(SKAction.repeatActionForever(spawnSequence), withKey: spawnKey) // run action with key so you can cancel it later

Than you have to add some logic of when you want to change the spawn duration property you created.

Time based could be a func like this you also call once in DidMoveToView

 func startDifficultyTimer() {

     let difficultyTimerKey = "DifficultyTimerKey"

     let action1 = SKAction.waitForDuration(30)
     let action2 = SKAction.runBlock { [unowned self] in

          guard self.spawnDuration > 0.2 else {  // set a min limit
              removeActionForKey(difficultyTimerKey) // if min duration has been reached than you might as well stop running this timer.

          self.spawnDuration -= 0.5 // reduce by half a second
          self.createSequentialEnemies() // spawn enemies again

     let sequence = SKAction.sequence([action1, action2])
     runAction(SKAction.repeatActionForever(sequence), withKey: difficultyTimerKey)

Hope this helps