Using Decreasing Variable as NSTimeInterval in swift - ios

Question

I am trying to decrease a Double variable by 0.05 every second to speed up the function spawnEnemy() but I cannot find a way that works well. So, I am trying to pretty much "spawn" more enemies(UIButtons) in a shorter amount of time. Any help would be great and very appreciated. Thank you! My code below compiles fine but does not speed up the NSTimer controlling the function spawnEnemy()
import UIKit
class ViewController: UIViewController {
#IBOutlet weak var scoreLabel: UILabel!
var points: Int = 0
func randomPoint() -> CGPoint {
let randomPoint: CGPoint = CGPoint(x:CGFloat(arc4random()%320),y:CGFloat(568-arc4random()%390))
return randomPoint
}
func randomColor() -> UIColor {
let red = CGFloat(drand48())
let green = CGFloat(drand48())
let blue = CGFloat(drand48())
return UIColor(red: red, green: green, blue: blue, alpha: 1.0)
}
func spawnEnemy() {
let enemy: UIButton = UIButton(frame: CGRect(x: 160, y: 160, width: 100, height: 100))
enemy.backgroundColor = randomColor()
enemy.center = randomPoint()
enemy.addTarget(self, action: Selector("buttonPushed:"), forControlEvents: UIControlEvents.TouchUpInside)
self.view.addSubview(enemy)
}
func buttonPushed(sender : UIButton) {
if sender.frame.height < 50 || sender.frame.width < 50 {
sender.frame = CGRectMake(sender.frame.origin.x, sender.frame.origin.y, 50, 50)
sender.backgroundColor = randomColor()
sender.center = randomPoint()
return
}
sender.backgroundColor = UIColor.blackColor()
points = points + 1
scoreLabel.textAlignment = .Center
scoreLabel.text = "\(points)"
scoreLabel.backgroundColor = UIColor.blackColor()
}
func decreaseDouble() -> Double {
var num: Double = 2.0
num = num - 0.05
return num
}
override func viewDidLoad() {
super.viewDidLoad()
NSTimer.scheduledTimerWithTimeInterval(decreaseDouble(), target: self, selector: Selector("spawnEnemy"), userInfo: nil, repeats: true)
NSTimer.scheduledTimerWithTimeInterval(1, target: self, selector: Selector("decreaseDouble"), userInfo: nil, repeats: false)
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
}
Below is my new code. Any finals things or should this work? I also added a while statement so you can only receive points while the enemy is not black,otherwise you could just keep clicking on wherever enemies have been spawned(but were clicked) and keep getting points. However, now when i run the application two enemies are already spawned but i can still click on them(only being allowed to get two points)
import UIKit
class ViewController: UIViewController {
#IBOutlet weak var scoreLabel: UILabel!
var points: Int = 0
func randomPoint() -> CGPoint {
let randomPoint: CGPoint = CGPoint(x:CGFloat(arc4random()%320),y:CGFloat(568-arc4random()%390))
return randomPoint
}
func randomColor() -> UIColor {
let red = CGFloat(drand48())
let green = CGFloat(drand48())
let blue = CGFloat(drand48())
return UIColor(red: red, green: green, blue: blue, alpha: 1.0)
}
func spawnEnemy() {
let enemy: UIButton = UIButton(frame: CGRect(x: 160, y: 160, width: 100, height: 100))
enemy.backgroundColor = randomColor()
enemy.center = randomPoint()
enemy.addTarget(self, action: Selector("buttonPushed:"), forControlEvents: UIControlEvents.TouchUpInside)
self.view.addSubview(enemy)
}
func buttonPushed(sender : UIButton) {
if sender.frame.height < 50 || sender.frame.width < 50 {
sender.frame = CGRectMake(sender.frame.origin.x, sender.frame.origin.y, 50, 50)
sender.backgroundColor = randomColor()
sender.center = randomPoint()
return
}
while sender.backgroundColor != UIColor.blackColor() {
points = points + 1
scoreLabel.textAlignment = .Center
scoreLabel.text = "\(points)"
scoreLabel.backgroundColor = UIColor.blackColor()
sender.backgroundColor = UIColor.blackColor()
}
delayTime -= 0.05
}
var delayTime: Double = 2.0
override func viewDidLoad() {
super.viewDidLoad()
delayTime = 2.0
NSTimer.scheduledTimerWithTimeInterval(2.0, target: self, selector: Selector("spawnEnemy"), userInfo: nil, repeats: false)
NSTimer.scheduledTimerWithTimeInterval(delayTime, target: self, selector: Selector("spawnEnemy"), userInfo: nil, repeats: true)
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}

Answer 1

Repeating NSTimers always fire on the same interval once you start them.
If you want to use a decreasing interval then instead of a repeating timer I suggest use use a single "one-shot" timer (not 2 timers). Create the timer with repeats:false. Then in your timer method (spawnEnemy, in your case) decrement your time interval and use it to create a new timer (also with repeats:false) using the new, shorter interval and calling the same method.
Your decreaseDouble function isn't going to work as written. It will always return the same value of 2.0 - 0.05, since you set num to 2.0 each time the function called. Instead get rid of the decreaseDouble function. Create an instance variable delayValue and assign it a value (2.0, for example) in your viewDidLoad. Then just subtract 0.05 from it each time spawnEnemy is called, spawn a new enemy, and create a new timer if delayValue hasn't gotten too small. (When delayValue gets really small you're going to be spawning 10 enemies a second. Eventually delayValue will go to zero, and a timer interval should not be <= 0.0.

Answer 2

You have the right idea. I would use the repeating timer as a 'tick' and then keep two properties - One is the tick count and the other is the tick count before a new enemy is spawned. By decreasing the latter you can speed up the rate of spawning.
Something like this
import UIKit
class ViewController: UIViewController {
#IBOutlet weak var scoreLabel: UILabel!
var points: Int = 0
var tickCount=0
var spawnRate=100 // Spawn every 10 seconds to start with
var spawnTimer:NSTimer!
override func viewDidLoad() {
super.viewDidLoad()
self.tickCount=self.spawnRate
self.spawnTimer=NSTimer.scheduledTimerWithTimeInterval(0.1, target: self, selector: Selector("tick"), userInfo: nil, repeats: true)
}
func tick() {
if (--tickCount == 0) {
self.spawnEnemy()
self.spawnRate=spawnRate - 2 // Change this to determine how quickly the spawn rate increases
self.tickCount=self.spawnRate
}
}
You can modify the tick rate and tick decrement amounts as required to give you the range you are after