"if" statement, condition will never be executed - swift

Question

I thought I was good with if statements but apparently Im still missing something. In the line timer.invalidate() the compiler complains
Will never be executed
As far as I can tell my syntax is correct.
#IBAction func button(_ sender: Any) {
let timer = Timer.scheduledTimer(timeInterval:0.2 , target: self, selector: #selector(ViewController.imageSwitch) , userInfo: nil, repeats: true)
var buttonState = false
if buttonState == true {
timer.invalidate()
buttonState = false
}
if buttonState == false {
timer.fire()
buttonState = true
}
}

Answer 1

You have to move the declaration of buttonState out of the method. And then simplify the if conditions:
var buttonState = false
#IBAction func button(_ sender: Any) {
let timer = Timer.scheduledTimer(timeInterval:0.2 , target: self, selector: #selector(ViewController.imageSwitch) , userInfo: nil, repeats: true)
if buttonState {
timer.invalidate()
buttonState = false
} else {
timer.fire()
buttonState = true
}
}
You should additionally ask yourself what the methods is even supposed to do, do you want the buttonState to continously switch from true to false and back or do you want it to do something else (like switching to to another value after a delay)? In the first case you should declare the timer outside the method and let it run there, never invalidate it - in the second case you should move the timer declaration inside the else block and turn repeat off. In both cases you should probably remove the timer.invalidate() and timer.fire() calls.

Answer 2

Full solution :
var timerState = false
var timer = Timer()
#IBAction func button(_ sender: Any) {
if timerState == false {
timer.invalidate()
timer = Timer.scheduledTimer(timeInterval:0.2 , target: self, selector: #selector(ViewController.imageSwitch) , userInfo: nil, repeats: true)
timerState = true
} else {
timer.invalidate()
timerState = false