Adding values to timer in Swift - swift

Question

I am creating a game where the user scores, the timer countdown need to be updated to add 2 seconds to it. I cannot seem to get this working. Other solutions online says that I need to invalidate the current timer and create a new one. How can I do that? The timer starts at 15 seconds, and I need to add 2 seconds in an if condition statement.
#objc func counter(){
seconds -= 1
countDownLabel.text = String(seconds)
if (seconds == 0){
timer.invalidate()
}
}
func updatetimer(){
seconds += 2
}
func activatetimer(){
timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(ViewController.counter), userInfo: nil, repeats: true)
}

Answer 1

I recommend to use a DispatchSource timer which can be restarted reliably right before adding the seconds. If the number of seconds just has expired nothing will happen.
var timer : DispatchSourceTimer?
func activatetimer() {
if timer != nil { return }
timer = DispatchSource.makeTimerSource(queue: DispatchQueue.global())
timer!.schedule(deadline:.now() + .seconds(1), repeating: 1.0)
timer!.setEventHandler {
self.seconds -= 1
DispatchQueue.main.async {
self.countDownLabel.text = String(self.seconds)
}
if self.seconds == 0 {
self.timer?.cancel()
self.timer = nil
}
}
timer!.resume()
}
func updatetimer(){
if let timer = timer {
timer.schedule(deadline:.now() + .seconds(1), repeating: 1.0)
seconds += 2
}
}

Answer 2

The Timer is not the key to the problem, the Timer is simply an opportunity to "check" how long the it's been running.
The real key is knowing how long the Timer has been running and how long it should be allowed to run (ie the duration), from this you can calculate how much time is left.
This then allows you to change the duration without having to do anything else.
Please take note that my timer is decreasing
Which is irrelevant. Basically you have several pieces of information...
You know: When the Timer was started
You can calculate: The amount of time the timer has been running (the difference between the start time and now)
You can calculate: The remaining time (difference between running time and the allowable duration)
It's all just basic time/duration functionality. The Timer just provides you means to "check" periodically how long the timer has been running
... As "rough" example...
var startedAt: Date?
var duration: TimeInterval = 5.0
var timer: Timer?
// This is just the label you want to update
#IBOutlet weak var durationLabel: UILabel!
// Convince duration formatter
var durationFormatter: DateComponentsFormatter = {
let formatter = DateComponentsFormatter()
formatter.allowedUnits = [.second]
formatter.unitsStyle = .abbreviated
return formatter
}()
// Stop the clock
func stop() {
timer?.invalidate()
timer = nil
startedAt = nil
}
// Start the clock
func start() {
stop() // Just make sure
startedAt = Date()
timer = Timer.scheduledTimer(timeInterval: 0.5, target: self, selector: #selector(tick(_:)), userInfo: nil, repeats: true)
}
// The check in
#objc func tick(_ timer: Timer) {
// Is the timer running?
guard let startedAt = startedAt else {
stop()
return
}
// How long has the timer been running
let runningTime = Date().timeIntervalSince(startedAt)
// Has time run out yet
if runningTime >= duration {
durationLabel.text = "Time ran out"
stop()
} else {
// Update the label with the remaining amount of time...
durationLabel.text = durationFormatter.string(from: duration - runningTime)
}
}
// Add more time to the duration...
#IBAction func moreTime(_ sender: Any) {
duration += 2.0
}
Playground example...
This is slightly modified version used to test the idea in Playground
import UIKit
import PlaygroundSupport
class Clock {
var startedAt: Date?
var duration: TimeInterval = 10.0
var timer: Timer?
var durationFormatter: DateComponentsFormatter = {
let formatter = DateComponentsFormatter()
formatter.allowedUnits = [.second]
formatter.unitsStyle = .abbreviated
return formatter
}()
func stop() {
timer?.invalidate()
timer = nil
startedAt = nil
}
func start() {
stop()
startedAt = Date()
timer = Timer.scheduledTimer(timeInterval: 1.0, target: self, selector: #selector(tick(_:)), userInfo: nil, repeats: true)
}
#objc func tick(_ timer: Timer) {
report()
}
func report() {
guard let startedAt = startedAt else {
stop()
return
}
let runningTime = Date().timeIntervalSince(startedAt)
print(">> Duration = \(duration); Running time = \(runningTime)")
if runningTime >= duration {
print("Time ran out")
PlaygroundPage.current.needsIndefiniteExecution = false
stop()
} else {
print(durationFormatter.string(from: duration - runningTime))
}
}
func moreTime(_ sender: Any) {
duration += 2.0
}
}
PlaygroundPage.current.needsIndefiniteExecution = true
let clock = Clock()
clock.start()
DispatchQueue.main.asyncAfter(wallDeadline: .now() + 2.0) {
print("++")
clock.moreTime("")
clock.report()
DispatchQueue.main.asyncAfter(wallDeadline: .now() + 2.0) {
print("++")
clock.moreTime("")
clock.report()
}
}
When I run it, it outputs...
>> Duration = 10.0; Running time = 1.0034409761428833
Optional("8s")
>> Duration = 10.0; Running time = 2.0030879974365234
Optional("7s")
++
>> Duration = 12.0; Running time = 2.018252968788147
Optional("9s")
>> Duration = 12.0; Running time = 3.002920985221863
Optional("8s")
>> Duration = 12.0; Running time = 4.002920985221863
Optional("7s")
++
>> Duration = 14.0; Running time = 4.035009980201721
Optional("9s")
>> Duration = 14.0; Running time = 5.003154993057251
Optional("8s")
>> Duration = 14.0; Running time = 6.002910017967224
Optional("7s")
>> Duration = 14.0; Running time = 7.002930045127869
Optional("6s")
>> Duration = 14.0; Running time = 8.003202080726624
Optional("5s")
>> Duration = 14.0; Running time = 9.002938032150269
Optional("4s")
>> Duration = 14.0; Running time = 10.002840995788574
Optional("3s")
>> Duration = 14.0; Running time = 11.002991080284119
Optional("2s")
>> Duration = 14.0; Running time = 12.002726078033447
Optional("1s")
>> Duration = 14.0; Running time = 13.003712058067322
Optional("0s")
>> Duration = 14.0; Running time = 14.002851009368896
Time ran out
As you can see, each time moreTime is called (look for the ++ output), 2 seconds is added to the duration. The Clock started with 10 seconds, but ended up running a total of 14 seconds