How to call function on time? Also How to Call only once time in swift 3?
i need to call one function one time only, so how can possible to call function only one time like after 3 seconds?
You can do something like,
DispatchQueue.main.asyncAfter(deadline: .now() + 3) {
yourFunction() // call your functin here
}
You can also use DispatchQueue.global().asyncAfter if you don't want to perform your task on main thread!
And refer this post to manage it one time only!
private let _onceToken = NSUUID().uuidString
DispatchQueue.once(token: _onceToken) {
print( "Do This Once!" )
DispatchQueue.main.asyncAfter(deadline: .now() + 3) {
yourFunction() // call your functin here
}
}
It will execute your method only once and delay your method for 3 seconds.
For start timer:
var timerUpdateArray:Timer!
func callTimer(){
self.timerUpdateArray = Timer.scheduledTimer(timeInterval: 1,
target: self, selector: #selector(yourFunc),
userInfo: nil, repeats: true)
}
For stop timer:
self.timerUpdateArray.invalidate()
I want to call the method func adjustmentBestSongBpmHeartRate() every 1.1 second. I used Timer, but it doesn't work. I have read the document and found a lot of sample code, it still does work! Is there anything I missed?
timer = Timer.scheduledTimer(timeInterval: 1.1, target: self, selector: #selector(self.adjustmentBestSongBpmHeartRate), userInfo: nil, repeats: false)
timer.fire()
func adjustmentBestSongBpmHeartRate() {
print("frr")
}
I found that creating the timer in an OperationQueue Operation did not work. I assume this is because there is no runloop.
Therefore, the following code fixed my problem:
DispatchQueue.main.async {
// timer needs a runloop?
self.timeoutTimer = Timer.scheduledTimer(timeInterval: self.timeout, target: self, selector: #selector(self.onTimeout(_:)), userInfo: nil, repeats: false)
}
Timer methods with a selector are supposed to have one parameter: The timer itself. Thus your code should really look like this: 1
Timer.scheduledTimer(timeInterval: 1.1,
target: self,
selector: #selector(self.adjustmentBestSongBpmHeartRate(_:),
userInfo: nil,
repeats: false)
#objc func adjustmentBestSongBpmHeartRate(_ timer: Timer) {
print("frr")
}
Note that if your app only runs on iOS >= 10, you can use the new method that takes a block to invoke rather than a target/selector. Much cleaner and more type-safe:
class func scheduledTimer(withTimeInterval interval: TimeInterval,
repeats: Bool,
block: #escaping (Timer) -> Void) -> Timer
That code would look like this:
timer = Timer.scheduledTimer(withTimeInterval: 1.1,
repeats: false) {
timer in
//Put the code that be called by the timer here.
print("frr")
}
Note that if your timer block/closure needs access to instance variables from your class you have to take special care with self. Here's a good pattern for that sort of code:
timer = Timer.scheduledTimer(withTimeInterval: 1.1,
repeats: false) {
//"[weak self]" creates a "capture group" for timer
[weak self] timer in
//Add a guard statement to bail out of the timer code
//if the object has been freed.
guard let strongSelf = self else {
return
}
//Put the code that be called by the timer here.
print(strongSelf.someProperty)
strongSelf.someOtherProperty = someValue
}
Edit (updated 15 December)
1: I should add that the method you use in the selector has to use Objective-C dynamic dispatch. In Swift 4 and later, the individual methods you reference must be tagged with the #objc tag. In previous versions of Swift you could also declare the entire class that defines the selector with the #objc qualifier, or you could make the class that defined the selector a subclass of NSObject or any class that inherits from NSOBject. (It's quite common to define the method the timer calls inside a UIViewController, which is a subclass of NSObject, so it used to "just work".
Swift 3
In my case it worked after I added to my method the #obj prefix
Class TestClass {
private var timer: Timer?
func start() {
guard timer == nil else { return }
timer = Timer.scheduledTimer(timeInterval: 60, target: self, selector: #selector(handleMyFunction), userInfo: nil, repeats: false)
}
func stop() {
guard timer != nil else { return }
timer?.invalidate()
timer = nil
}
#objc func handleMyFunction() {
// Code here
}
}
Try this -
if #available(iOS 10.0, *) {
self.timer = Timer.scheduledTimer(withTimeInterval: 0.2, repeats: false, block: { _ in
self.update()
})
} else {
self.timer = Timer.scheduledTimer(timeInterval: 0.2, target: self, selector: #selector(self.update), userInfo: nil, repeats: false)
}
Mostly the problem must have been because of iOS version of mobile.
Swift 5, Swift 4 Simple way only call with Dispatch Queue Async
DispatchQueue.main.async
{
self.andicator.stopAnimating()
self.bgv.isHidden = true
Timer.scheduledTimer(withTimeInterval: 1.0, repeats: false, block: { _ in
obj.showAlert(title: "Successfully!", message: "Video save successfully to Library directory.", viewController: self)
})
}
I have solved the question asked by myself.
I'm using apple watch to control my iphone app.
I try to press a button on apple watch to present a new viewcontroller on iphone.
When I write Timer in override func viewDidLoad(), Timer doesn't work. I move Timer to override func viewWillAppear() it works.
I think maybe there's something wrong with controlling by apple watch
I found that if you try to initialize the timer directly at the class-level, it won't work if you're targeting a selector in that same class. When it fires, it can't find the selector.
To get around this, I only initialize the timer after the object containing the selector has been initialized. If it's in the same class, put the initialization code in the ViewDidLoad or similar. Just not in the initializer. Then it will work. No dispatch queue needed.
Also, you do not need to use a selector that accepts the timer as a parameter. You can, but contrary to the answer with a ton of votes, that's not actually true, or more specifically, it works fine for me without it, just as you have it without it.
By the way, I think the reason the dispatch queue worked is because you're forcing the timer to be created after the object was initializing, confirming my above statement.
let timer:Timer?
override func viewDidLoad(){
super.viewDidLoad()
timer = Timer.scheduledTimer(timeInterval: 1.1, target: self, selector: #selector(adjustmentBestSongBpmHeartRate), userInfo: nil, repeats: false)
timer.fire()
}
func adjustmentBestSongBpmHeartRate() {
print("frr")
}
Note: This is code typed from memory, not copied from Xcode so it may not compile, but hopefully you get the idea.
Swift3
var timer = Timer()
timer = Timer.scheduledTimer(timeInterval: 5, target: self, selector: #selector(self.compruebaConexion), userInfo: nil, repeats: true)
my two cents.
I read about "didLoad" and when invoking it.
so we can use a delay:
class ViewController: UIViewController {
var timer: Timer?
override func viewDidLoad() {
super.viewDidLoad()
startTimer()
}
final func killTimer(){
self.timer?.invalidate()
self.timer = nil
}
final private func startTimer() {
// make it re-entrant:
// if timer is running, kill it and start from scratch
self.killTimer()
let fire = Date().addingTimeInterval(1)
let deltaT : TimeInterval = 1.0
self.timer = Timer(fire: fire, interval: deltaT, repeats: true, block: { (t: Timer) in
print("hello")
})
RunLoop.main.add(self.timer!, forMode: RunLoopMode.commonModes)
}
I have just started to learn swift 2 and I am testing a few things in an Xcode 'playground'. When a create an instance of the 'pyx' (below) I am not seeing the console output I would expect. I am sure I have made a silly mistake but after staring at it for a while I cannot figure it out.
class zxy {
var gameTimer = NSTimer()
var counter = 0
init() {
gameTimer = NSTimer (timeInterval: 1, target: self, selector: "Run:", userInfo: nil, repeats: true)
}
func Run(timer : NSTimer) {
while(counter < 10){
print(counter)
counter++
}
timer.invalidate()
}
}
Thanks in advanced.
You have 2 problems with your code. As #glenstorey points out in his answer, you need to call the method scheduledTimerWithTimeInterval:target:selector:userInfo:repeats:, not the init method you're calling.
EDIT:
As #DanBeauleu says in his comment to my answer, the call would look like this in Swift:
NSTimer.scheduledTimerWithTimeInterval(
1,
target: self,
selector: "Run:",
userInfo: nil,
repeats: true)
The second problem is your Run method.
You don't want a while loop. That will repeat 10 times in a tiny fraction of a second the first time the timer fires, then invalidate the timer.
Your timer method needs to be changed like this:
func Run(timer : NSTimer)
{
if counter < 10
{
print(counter)
counter++
}
else
{
timer.invalidate()
}
}
(BTW, by strong convention, method/function names should start with a lower-case letter, so your Run function should be named run instead.)
You've created a NSTimer object, but that doesn't start the timer - just gets it ready to go. Use scheduledTimerWithTimeInterval to create and start the timer.
I am trying to use the NSTimer to increment the progress bar in my app when recording voice (see the screenshot)
let timedClock = NSTimer.scheduledTimerWithTimeInterval(1, target: self, selector: Selector("Counting:"), userInfo: nil, repeats: true)
internal func Counting(timer: NSTimer!) {
if timeCount == 0 {
//self.timedClock = nil
stopRecording(self) //performs segue to another view controller
} else {
timeCount--;
self.timer.text = "\(timeCount)"
}
print("counting called!")
progressBar.progress += 0.2
}
The progress bar works only for the first time after I compile and run the project. When the recording is finished, the app performs segue to another view controller to play the recorded audio. However, when I go back to the view for recording, the timer/progress bar automatically runs. I suspect the NSTimer object is still alive on the NSRunLoop. So I was wondering how to prevent the NSTimer from automatically running.
Inspired by the answer in this SO thread, I tried the following, but the NSTimer still automatically runs.
let timedClock = NSTimer(timeInterval: 1, target: self, selector: "Counting:", userInfo: nil, repeats: true)
NSRunLoop.currentRunLoop().addTimer(timedClock, forMode: NSRunLoopCommonModes)
This happens because when your controller created it's properties are automatically initialized. According to Apple Docs (and method's name) scheduledTimerWithTimeInterval create and return scheduled timer. So if you only want create your timer and call it by trigger function use it like this:
class MyClass {
var timer: NSTimer?
...
func enableTimer() {
timer = NSTimer.scheduledTimerWithTimeInterval(1, target: self, selector: Selector("Counting:"), userInfo: nil, repeats: true)
}
func disableTimer() {
timer?.invalidate()
timer = nil
}
...
}
Sorry for the quick self-answer, as I just found out that I can use the invalidate() method to prevent the timer from automatically firing:
timedClock.invalidate()
Hope it helps someone in the future!
I am new to swift programming and I don't know how to call a method at regular interval of time. I have a demo app for service call but i don't know how can i call it at regular interval of time.
You can create an object of NSTimer() and call a function on definite time interval like this:
var updateTimer = NSTimer.scheduledTimerWithTimeInterval(15.0, target: self, selector: "callFunction", userInfo: nil, repeats: true)
this will call callFunction() every 15 sec.
func callFunction(){
print("function called")
}
Here is a simple example with start and stop functions:
private let kTimeoutInSeconds:NSTimeInterval = 60
private var timer: NSTimer?
func startFetching() {
self.timer = NSTimer.scheduledTimerWithTimeInterval(kTimeoutInSeconds,
target:self,
selector:Selector("fetch"),
userInfo:nil,
repeats:true)
}
func stopFetching() {
self.timer!.invalidate()
}
func fetch() {
println("Fetch called!")
}
If you get an unrecognized selector exception, make sure your class inherits from NSObject or else the timer's selector won't find the function!
Timer variant with a block (iOS 10, Swift 4)
let timer = Timer.scheduledTimer(withTimeInterval: 5, repeats: true) { (timer) in
print("I am called every 5 seconds")
}
Do not forget call invalidate method
timer.invalidate()
GCD approach (will tend to drift a bit late over time)
func repeatMeWithGCD() {
DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + 5) {
print("I am called every 5 seconds")
self.repeatMeWithGCD()//recursive call
}
}
Do not forget to create a return condition to prevent stackoverflow error