Timer.scheduledTimer Swift 3 pre-iOS 10 compatibility

Question

I need to schedule a Timer for firing a function every second but I see that in Xcode 8 beta 3 the scheduledTimer is only available for iOS 10.

Is there any alternative for using the timer in iOS 9 or previous versions?

Timer.scheduledTimer(withTimeInterval: 1, repeats: true, block: { (timer) in print("Hi!")})

Myriammyriameter

Answer 1

Solved using

Timer.scheduledTimer(timeInterval: 1,
                           target: self,
                         selector: #selector(self.updateTime),
                         userInfo: nil,
                          repeats: true)

Myriammyriameter

If you wish you can use if #available(iOS 10, *) { //iOS 10 code } else { //iOS 9 code } to support both depending on the OS version. – Zoometry

I needed to add write the target function like this: @objc func updateTime() {} – Etter

It's also worth looking at the lower posts to see how Timer's are stopped. It may not get removed from the run loop properly if it's not removed manually. – Electrode

Hy I am new to swift, just a basic question, what does userInfo represents in scheduledTimer function?? – Timpani

Hi @prasoonraj, I guess that it means that you can pass a dictionary with any useful information every time the timer is fired. – Myriammyriameter

Answer 2

Run a timer with swift3,

var timer: Timer?

func startTimer() {

    if timer == nil {
        timer = Timer.scheduledTimer(timeInterval: 3, target: self, selector: #selector(self.loop), userInfo: nil, repeats: true)
    }
}

func stopTimer() {
    if timer != nil {
        timer?.invalidate()
        timer = nil
    }
}

func loop() {
    let liveInfoUrl = URL(string: "http://192.168.1.66/api/cloud/app/liveInfo/7777")
    let task = URLSession.shared.dataTask(with: liveInfoUrl! as URL) {data, response, error in
        guard let data = data, error == nil else { return }
        print(String(data: data, encoding: String.Encoding(rawValue: String.Encoding.utf8.rawValue)) ?? "aaaa")
    }
    task.resume()
}

Release the timer when you not use it.

Once scheduled on a run loop, the timer fires at the specified interval until it is invalidated. A nonrepeating timer invalidates itself immediately after it fires. However, for a repeating timer, you must invalidate the timer object yourself by calling its invalidate() method.

Negress

Great job pointing out the .invalidate() end of Timer's, as well as the run loop. – Electrode

The nil check for timer is unnecessary. It is already an optional. – Tusk

Answer 3

Here is sample code workable with compatibility:

if #available(iOS 10.0, *) {
    Timer.scheduledTimer(withTimeInterval: 15.0, repeats: true){_ in
        // Your code is here:
        self.myMethod()
    }
} else {      
    Timer.scheduledTimer(timeInterval: 15.0, target: self, selector: #selector(self.myMethod), userInfo: nil, repeats: true)
}

//Your method or function:

// MARK: -  Method

@objc func myMethod() {
    print("Hi, How are you.")
}

Indira

Answer 4

Swift 3

func runCode(in timeInterval:TimeInterval, _ code:@escaping ()->(Void))
{
    DispatchQueue.main.asyncAfter(
        deadline: .now() + timeInterval,
        execute: code)
}

func runCode(at date:Date, _ code:@escaping ()->(Void))
{
    let timeInterval = date.timeIntervalSinceNow
    runCode(in: timeInterval, code)
}

func test()
{
    runCode(at: Date(timeIntervalSinceNow:2))
    {
        print("Hello")
    }

    runCode(in: 3.0)
    {
        print("World)")
    }
}

Tamtam

Answer 5

Updated for swift 3:

If you want to use Timer for some delay or any other purpose used below lines of code in your project;

// function defination:

func usedTimerForDelay()  {
    Timer.scheduledTimer(timeInterval: 0.3,
                         target: self,
                         selector: #selector(self.run(_:)),
                         userInfo: nil, 
                         repeats: false)
}

func run(_ timer: AnyObject) {
      print("Do your remaining stuff here...")

}

// function call:

self.usedTimerForDelay()

NOTE:- you can change the time interval as you want.

//Enjoy coding..!

Imitate

Answer 6

Timer.scheduledTimer

Put it in the main thread.

Crider

Answer 7

You can use the following simple shim to provide the new block-based Timers to pre-iOS 10:

class TimerShim {
    private var timer: Timer?
    private let block: (Timer) -> Void

    private init(timeInterval interval: TimeInterval, repeats: Bool, block: @escaping (Timer) -> Void) {
        self.block = block
        timer = Timer.scheduledTimer(timeInterval: interval, target: self, selector: #selector(timerDidFire), userInfo: nil, repeats: repeats)
    }

    class func scheduledTimer(withTimeInterval interval: TimeInterval, repeats: Bool, block: @escaping (Timer) -> Void) -> Timer {
        return TimerShim(timeInterval: interval, repeats: repeats, block: block).timer!
    }

    @objc private func timerDidFire() {
        block(timer!)
    }
}

Usage example:

TimerShim.scheduledTimer(withTimeInterval: 5, repeats: false) { _ in
    print("boom!")
}

Praemunire

Answer 8

The correct form is:

Timer.scheduledTimer(withTimeInterval: 2, repeats: false){_ in
   "Here your code method"
}

Powerdive

This is not running on iOS 9, but the question asked for < iOS 10 compatibility – Tamtam

This code is working on swift 4.2 also.. Thanx for it. – Schwenk