Wait For Duration Decreasing Parameter - swift

Question

I want to decreasing the parameter of SKAction.waitForDuration(X).
I'm using the Flappy Bird Tutorial (https://www.youtube.com/watch?v=RjUvEiNxWfc - see on minute 7) and I want to do something like
var timeToWait:Int = 8
let spawn = SKAction.runBlock({
() in
self.createWalls()
timeToWait--
})
let delay = SKAction.waitForDuration(timeToWait)
let SpawnDelay = SKAction.sequence([spawn, delay])
let spawnDelayForever = SKAction.repeatActionForever(SpawnDelay)
self.runAction(spawnDelayForever)
However, the parameter for waitForDuration is NSTimer and not a float. What could I do to change that parameter?
Thank you!

Answer 1

waitForDuration expects a value of type NSTimeInterval.
You can Type cast timeToWait when you pass it to the function:
let delay = SKAction.waitForDuration(NSTimeInterval(timeToWait))
By the way, your code seems to want to decrease the delay between each spawn but it will not do that because timeDelay is captured in your creation of the delay action and will not change that action's duration if you modify the variable afterward.
[EDIT]
Here's an example accelerates spawning interval (from 8 to 1) in cycles:
let spawn = SKAction.runBlock({ self.createWalls() })
var spawnCycle:[SKAction] = []
for timeToWait in (1...8).reverse()
{
spawnCycle.append(spawn)
spawnCycle.append(SKAction.waitForDuration(NSTimeInterval(timeToWait)))
}
self.runAction(SKAction.repeatActionForever(SKAction.sequence(spawnCycle)))