Swift call timer from ViewController - ios

Question

I have a TimerManager class that I would like to access in multiple ViewControllers but I can't figure out a good way to do it. My code is as follows:
class TimerManager {
private var timer: NSTimer
private var timeRemaining: Int
init(initialTime: Int) {
self.timer = NSTimer()
self.timeRemaining = initialTime
}
func startTimer() {
self.timer = NSTimer.scheduledTimerWithTimeInterval(1.0, target: self, selector: #selector(TimerManager.update), userInfo: nil, repeats: true)
}
func endTimer() {
self.timer.invalidate()
}
func getTimeRemaining() -> Int {
return self.timeRemaining
}
#objc func update() {
if self.timeRemaining > 0 {
self.timeRemaining = self.timeRemaining - 1
}
else {
endTimer()
}
}
}
In my ViewController I would like to be able to access my update() function to update a timer (which is a UILabel) on my actual page, but since my startTimer() function calls it every second, I don't know how to access update() every time it is called. I briefly looked into protocols but I'm not really sure how they work or if that would be useful in my case.
Any help would be appreciated!

Answer 1

As #sschale suggested, you can do this by using a singleton to ensure that you will be accessing the same instance anywhere in your code. To do this, you need to set the init to private and provide a static member variable to access your single instance.
class TimerManager
{
static let sharedInstance = TimerManager()
private var timer: NSTimer
private var timeRemaining: Int
private init()
{
let initialTime = 1
self.timer = NSTimer()
self.timeRemaining = initialTime
}
private init(initialTime: Int)
{
self.timer = NSTimer()
self.timeRemaining = initialTime
}
...
}
Then in your ViewControllers you can just call it like this:
TimerManager.sharedInstance.startTimer()

Answer 2

class TimerManager {
private var timer: NSTimer
private var timeRemaining: Int
private var intervalBlock: (TimerManager -> ())?
init(initialTime: Int) {
self.timer = NSTimer()
self.timeRemaining = initialTime
}
func startTimer(intervalBlock: (TimerManager -> ())? = nil) {
self.intervalBlock = self
self.timer = NSTimer.scheduledTimerWithTimeInterval(1.0, target: self, selector: #selector(TimerManager.update), userInfo: nil, repeats: true)
}
func endTimer() {
self.intervalBlock = nil
self.timer.invalidate()
}
func getTimeRemaining() -> Int {
return self.timeRemaining
}
#objc func update() {
if self.timeRemaining > 0 {
self.timeRemaining = self.timeRemaining - 1
intervalBlock()
}
else {
intervalBlock()
endTimer()
}
}
}

Answer 3

Below is one of the best implementations of Timer on the background queue I found from this article
class RepeatingTimer {
let timeInterval: TimeInterval
init(timeInterval: TimeInterval) {
self.timeInterval = timeInterval
}
private lazy var timer: DispatchSourceTimer = {
let t = DispatchSource.makeTimerSource()
t.schedule(deadline: .now() + self.timeInterval, repeating: self.timeInterval)
t.setEventHandler(handler: { [weak self] in
self?.eventHandler?()
})
return t
}()
var eventHandler: (() -> Void)?
private enum State {
case suspended
case resumed
}
private var state: State = .suspended
deinit {
timer.setEventHandler {}
timer.cancel()
resume()
eventHandler = nil
}
func resume() {
if state == .resumed {
return
}
state = .resumed
timer.resume()
}
func suspend() {
if state == .suspended {
return
}
state = .suspended
timer.suspend()
}
}
Usage: -
In any of your ViewControllers
For example: -
class MyViewController: UIViewController {
// MARK: - Properties
var timer: RepeatingTimer!
// MARK: - ViewController LifeCycle
override func viewDidLoad() {
super.viewDidLoad()
timer = RepeatingTimer(timeInterval: 1)
timer.eventHandler = {
print("Timer called")
}
}