Swift: Issue with my NSTimer? - swift

Question

So in general terms, this is what i want my program to do: music will play, randomly generate a number between 3 and 12, then set a timer according to that number, when the timer is finished stop the music for 1 second, then after that one second, play the music again(and repeat the process, generate random number...)
This is the code I have written to do so, it works great the first run, but the second run it starts calling the functions at a faster rate(not following the timer) and sometimes in a different order(you can test this by looking at the print out)
var randomTimeInteger = Int()
var stopMusicTimer = NSTimer()
var startMusicTimer = NSTimer()
override func viewDidLoad(){
playMusic()
}
//Call to get random interger
func generateRandomInteger(){
print("Inside generate random integer")
let lower = 3
let upper = 12
randomTimeInteger = lower + Int(arc4random_uniform(UInt32(upper - lower + 1)))
print("Random Integer is : \(randomTimeInteger)")
initiateTimer()
}
//Start the timer
func initiateTimer() {
print("Inside initate Timer")
//Set Timer
stopMusicTimer = NSTimer.scheduledTimerWithTimeInterval(Double(randomTimeInteger), target: self, selector: "stopMusic", userInfo: nil, repeats: true)
}
//Stop the music
func stopMusic(){
print("Inside stop music")
GameViewController.backgroundAudio?.stop()
startMusicTimer = NSTimer.scheduledTimerWithTimeInterval(3.0, target: self, selector: "playMusic", userInfo: nil, repeats: true)
}
func playMusic(){
print("Inside play music")
GameViewController.backgroundAudio?.play()
generateRandomInteger()
}
Any idea what the problem is? Or if there is a better way to do so? PLEASE HELP!

Answer 1

You have one timer that tries to stop the music every 3 to 12 seconds. And sometimes you create a timer that tries to start the music every 3 seconds. And sometimes you create more of these timers. So eventually you have lots and lots of timers that try starting and stopping the music at random time.
To stop a repeating timer, call invalidate.
And don't initialise the timers as you do, NSTimer() returns nothing useful. Just declare the variables as NSTimer?

Answer 2

There are really numerous viable approaches.
Starting from the top, I would sketch the design as follows:
func playMusic(completion: (ErrorType?)->()) {
play(randomDuration()) { error in
if error != nil {
completion(error)
return
}
delay(1.0, f: play)
}
}
func randomDuration() -> Double {...}
func play(duration: Double, completion: (ErrorType?)->()) {
let player = Player(...)
player.resume()
delay(duration) {
player.suspend()
completion(nil)
}
}
Function delay(_:f:) is implemented in terms of dispatch_after.
You will probably notice, that playMusic runs indefinitely. This is by your requirements, but in practice you need a way to stop it.