Timer.scheduledTimer not firing - swift

Question

I am trying to calculate the time it takes a vehicle to go between two checkpoints. I have setup the following timer to achieve this.
func startTimer() {
if hasStarted == true && timerStarted == false {
print("Timing started!")
gameTimer = Timer.scheduledTimer(timeInterval: 0.001, target: self, selector: (#selector(activeTiming)), userInfo: nil, repeats: true)
timerStarted = true
}
}
#objc func activeTiming() {
print("Active timing block")
if(hasFinished == false) {
gameTime = gameTime + 0.001
print("Add time succeeded")
} else {
gameTimer?.invalidate()
}
}
The expected output would be the following:
Timing started!
Active timing block
Add time succeeded
Add time succeeded ... etc
The actual output:
Timing started!
So it would appear that the startTimer is properly being called but the timer is not firing the activeTiming block of code. Any suggestions would be extremely helpful. Thank you for your help in advance.

Answer 1

Posting this code as it is what I'm using, but I’m no expert on Swift, so your mileage may vary!
class PerformanceTest {
var name: String = ""
var tolerance: Int64 = 0
var lastTime: Int64 = 0
var thisTime: Int64 = 0
var delta: Int64 = 0
var percent: Float = 0
func setTolerance(vName: String, vTolerance: Int64) {
name = vName
tolerance = vTolerance
}
func reset() {
delta = 0
percent = Float((Float(delta) / Float(tolerance))) * 100
//high = 0
}
func start() {
lastTime = Date().toMillis()
}
func finish() {
thisTime = Date().toMillis()
let vDelta = thisTime - lastTime
if(vDelta > delta) {
delta = vDelta
percent = Float((Float(delta) / Float(tolerance))) * 100
if(delta > tolerance) {
print("Performance Indicator: \(name) Above Tolerance" + String(format: "%3.0f", percent) + "%")
}
}
}
func display() -> String {
//high = delta
//print("\(vString) Tolerance: \(tolerance) Max: \(high)")
return String(format: "%3.0f", percent) + "% |"
}
}
extension Date {
func toMillis() -> Int64! {
return Int64(self.timeIntervalSince1970 * 1000)
}
Usage:
var performanceDefenseLoop = PerformanceTest()
performanceDefenseLoop.setTolerance(vName: "DefenseLoop", vTolerance: 150)
func timeToUpdateDefenses()
{
performanceDefenseLoop.start()
defesensesLoop()
performanceDefenseLoop.finish()
print("\(performanceDefenseLoop.Display())"
}
// To reset
performanceDefenseLoop.reset()
Be sure to start timers in the main thread!

Answer 2

I also faced a similar issue where the timer body was not getting called. I found out that the timer was getting scheduled from a background thread instead of the main thread. Wrapping it in DispatchQueue.main.async fixed it.
DispatchQueue.main.async {
self.pingTimer = Timer.scheduledTimer(withTimeInterval: timerInterval, repeats: true, block: { [weak self] timer in
//
Logger.shared.log(.anyCable, .debug, "timer run")
self?.sendPing(sender: self)
})
}

Answer 3

Your code works for me, but that isn't how you want to time an event because the Timer isn't that accurate, and you are wasting a lot of computing time (read battery).
Instead, I suggest the following approach:
When the event starts, record the start time:
let startTime = Date()
When the event ends, compute the elapsed time:
let elapsedTime = Date().timeIntervalSince(startTime)
elapsedTime will be in seconds (including fractional seconds).