Related
Could someone explain to me why this isn't working
class MyClass{
#objc func doSomething(){
print("I did something");
}
}
let timer = Timer.scheduledTimer(timeInterval: 1.0, target: MyClass, selector: #selector(doSomething), userInfo: nil, repeats: true)
----EDIT--------
Found out that this works instead
let timer = Timer.scheduledTimer(timeInterval: 1.0, target: MyClass(), selector: #selector(MyClass.doSomething), userInfo: nil, repeats: false)
Could someone explain why target needs to be MyClass() and not MyClass and why it needs to be MyClass.doSomething and not doSomething. Cos I thought the target becomes the scope for the selector
Correct Code
var timer : Timer?
func timerstarter(){
timer = Timer.scheduledTimer(timeInterval: 1.0, target: self, selector: #selector(doSomething), userInfo: nil, repeats: true)
}
#objc func doSomething(){
print("I did something");
}
I tried
var timer = NSTimer()
timer(timeInterval: 0.01, target: self, selector: update, userInfo: nil, repeats: false)
But, I got an error saying
'(timeInterval: $T1, target: ViewController, selector: () -> (), userInfo: NilType, repeats: Bool) -> $T6' is not identical to 'NSTimer'
This will work:
override func viewDidLoad() {
super.viewDidLoad()
// Swift block syntax (iOS 10+)
let timer = Timer(timeInterval: 0.4, repeats: true) { _ in print("Done!") }
// Swift >=3 selector syntax
let timer = Timer.scheduledTimer(timeInterval: 0.4, target: self, selector: #selector(self.update), userInfo: nil, repeats: true)
// Swift 2.2 selector syntax
let timer = NSTimer.scheduledTimerWithTimeInterval(0.4, target: self, selector: #selector(MyClass.update), userInfo: nil, repeats: true)
// Swift <2.2 selector syntax
let timer = NSTimer.scheduledTimerWithTimeInterval(0.4, target: self, selector: "update", userInfo: nil, repeats: true)
}
// must be internal or public.
#objc func update() {
// Something cool
}
For Swift 4, the method of which you want to get the selector must be exposed to Objective-C, thus #objc attribute must be added to the method declaration.
Repeated event
You can use a timer to do an action multiple times, as seen in the following example. The timer calls a method to update a label every half second.
Here is the code for that:
import UIKit
class ViewController: UIViewController {
var counter = 0
var timer = Timer()
#IBOutlet weak var label: UILabel!
// start timer
#IBAction func startTimerButtonTapped(sender: UIButton) {
timer.invalidate() // just in case this button is tapped multiple times
// start the timer
timer = Timer.scheduledTimer(timeInterval: 0.5, target: self, selector: #selector(timerAction), userInfo: nil, repeats: true)
}
// stop timer
#IBAction func cancelTimerButtonTapped(sender: UIButton) {
timer.invalidate()
}
// called every time interval from the timer
func timerAction() {
counter += 1
label.text = "\(counter)"
}
}
Delayed event
You can also use a timer to schedule a one time event for some time in the future. The main difference from the above example is that you use repeats: false instead of true.
timer = Timer.scheduledTimer(timeInterval: 2.0, target: self, selector: #selector(delayedAction), userInfo: nil, repeats: false)
The above example calls a method named delayedAction two seconds after the timer is set. It is not repeated, but you can still call timer.invalidate() if you need to cancel the event before it ever happens.
Notes
If there is any chance of starting your timer instance multiple times, be sure that you invalidate the old timer instance first. Otherwise you lose the reference to the timer and you can't stop it anymore. (see this Q&A)
Don't use timers when they aren't needed. See the timers section of the Energy Efficiency Guide for iOS Apps.
Related
How to work with dates and time in Swift
Updated to Swift 4, leveraging userInfo:
class TimerSample {
var timer: Timer?
func startTimer() {
timer = Timer.scheduledTimer(timeInterval: 5.0,
target: self,
selector: #selector(eventWith(timer:)),
userInfo: [ "foo" : "bar" ],
repeats: true)
}
// Timer expects #objc selector
#objc func eventWith(timer: Timer!) {
let info = timer.userInfo as Any
print(info)
}
}
As of iOS 10 there is also a new block based Timer factory method which is cleaner than using the selector:
_ = Timer.scheduledTimer(withTimeInterval: 5, repeats: false) { timer in
label.isHidden = true
}
Swift 5
I personally prefer the Timer with the block closure:
Timer.scheduledTimer(withTimeInterval: 1, repeats: false) { (_) in
// TODO: - whatever you want
}
Swift 3, pre iOS 10
func schedule() {
DispatchQueue.main.async {
self.timer = Timer.scheduledTimer(timeInterval: 20, target: self,
selector: #selector(self.timerDidFire(timer:)), userInfo: nil, repeats: false)
}
}
#objc private func timerDidFire(timer: Timer) {
print(timer)
}
Swift 3, iOS 10+
DispatchQueue.main.async {
self.timer = Timer.scheduledTimer(withTimeInterval: 20, repeats: false) { timer in
print(timer)
}
}
Notes
It needs to be on the main queue
Callback function can be public, private, ...
Callback function needs to be #objc
Check with:
Swift 2
var timer = NSTimer.scheduledTimerWithTimeInterval(0.01, target: self, selector: Selector("update"), userInfo: nil, repeats: true)
Swift 3, 4, 5
var timer = Timer.scheduledTimer(timeInterval: 0.01, target: self, selector: #selector(self.update), userInfo: nil, repeats: true)
You will need to use Timer instead of NSTimer in Swift 3.
Here is an example:
Timer.scheduledTimer(timeInterval: 1,
target: self,
selector: #selector(YourController.update),
userInfo: nil,
repeats: true)
// #objc selector expected for Timer
#objc func update() {
// do what should happen when timer triggers an event
}
First declare your timer
var timer: Timer?
Then add line in viewDidLoad() or in any function you want to start the timer
timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(action), userInfo: nil, repeats: false)
This is the func you will callback it to do something it must be #objc
#objc func action () {
print("done")
}
for swift 3 and Xcode 8.2
(nice to have blocks, but if You compile for iOS9 AND want userInfo):
...
self.timer = Timer(fireAt: fire,
interval: deltaT,
target: self,
selector: #selector(timerCallBack(timer:)),
userInfo: ["custom":"data"],
repeats: true)
RunLoop.main.add(self.timer!, forMode: RunLoopMode.commonModes)
self.timer!.fire()
}
func timerCallBack(timer: Timer!){
let info = timer.userInfo
print(info)
}
SimpleTimer (Swift 3.1)
Why?
This is a simple timer class in swift that enables you to:
Local scoped timer
Chainable
One liners
Use regular callbacks
Usage:
SimpleTimer(interval: 3,repeats: true){print("tick")}.start()//Ticks every 3 secs
Code:
class SimpleTimer {/*<--was named Timer, but since swift 3, NSTimer is now Timer*/
typealias Tick = ()->Void
var timer:Timer?
var interval:TimeInterval /*in seconds*/
var repeats:Bool
var tick:Tick
init( interval:TimeInterval, repeats:Bool = false, onTick:#escaping Tick){
self.interval = interval
self.repeats = repeats
self.tick = onTick
}
func start(){
timer = Timer.scheduledTimer(timeInterval: interval, target: self, selector: #selector(update), userInfo: nil, repeats: true)//swift 3 upgrade
}
func stop(){
if(timer != nil){timer!.invalidate()}
}
/**
* This method must be in the public or scope
*/
#objc func update() {
tick()
}
}
timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(createEnemy), userInfo: nil, repeats: true)
And Create Fun By The Name createEnemy
fund createEnemy ()
{
do anything ////
}
In Swift 3 something like this with #objc:
func startTimerForResendingCode() {
let timerIntervalForResendingCode = TimeInterval(60)
Timer.scheduledTimer(timeInterval: timerIntervalForResendingCode,
target: self,
selector: #selector(timerEndedUp),
userInfo: nil,
repeats: false)
}
#objc func timerEndedUp() {
output?.timerHasFinishedAndCodeMayBeResended()
}
If you init method of timer
let timer = Timer(timeInterval: 3, target: self, selector: #selector(update(_:)), userInfo: [key : value], repeats: false)
func update(_ timer : Timer) {
}
then add it to loop using method other selector will not be called
RunLoop.main.add(timer!, forMode: .defaultRunLoopMode)
NOTE : If you are want this to repeat make repeats true and keep the reference of timer otherwise update method will not be called.
If you are using this method.
Timer.scheduledTimer(timeInterval: seconds, target: self, selector: #selector(update(_:)), userInfo: nil, repeats: true)
keep a reference for later use if repeats is true.
I tried to do in a NSObject Class and this worked for me:
DispatchQueue.main.asyncAfter(deadline: .now() + .milliseconds(300)) {
print("Bang!") }
NSTimer has been renamed to Timer in Swift 4.2.
this syntax will work in 4.2:
let timer = Timer.scheduledTimer(timeInterval: 1.0, target: self, selector: #selector(UIMenuController.update), userInfo: nil, repeats: true)
I'm not sure why but every time I run my application, my timer will not call the update function. I have tried everything: using #selector, adding a colon at the end of update, nothing is working. I have added a print statement inside my update to make sure that it reaches there, and the print statement never prints! I'm not sure why it isn't being called.... Help! P.S. I know selected is indeed one of the options in the if statement, I had a print statement for that and it's working.
if (selected == "05 seconds") {
count = 5
timer = Timer(timeInterval: 1.0, target: self, selector: Selector("update"), userInfo: nil, repeats: true)
}
else if (selected == "10 seconds") {
count = 10
timer = Timer(timeInterval: 1.0, target: self, selector: Selector("update"), userInfo: nil, repeats: true)
}
else if (selected == "20 seconds") {
count = 20
timer = Timer(timeInterval: 1.0, target: self, selector: Selector("update"), userInfo: nil, repeats: true)
}
else if (selected == "30 seconds") {
print("I'm here!")
count = 30
timer = Timer(timeInterval: 1.0, target: self, selector: Selector("update"), userInfo: nil, repeats: true)
}
else if (selected == "Single Shot") {
SendButton.isHidden = false
countDownLabel.isHidden = true
}
}
func update() {
print("Now I'm in update!")
count = count - 1;
countDownLabel.text = String(count)
}
The timer does not work, because the method you are using requires that the timer is explicitly added to the runloop.
Use the API which adds the timer implicitly to the runloop.
DispatchQueue.main.async {
timer = Timer.scheduledTimer(timeInterval: 1.0, target: self, selector: #selector(update), userInfo: nil, repeats: true)
}
PS: The #selector syntax is preferable because it checks the existence of the action method at compile time.
I want to implement NSTimer.scheduledTimerWithTimeInterval in Swift 3. I want to know the Replacement of
NSTimer.scheduledTimerWithTimeInterval(0.35, target: self, selector: #selector(createEnemy), userInfo: nil, repeats: true)
as we used it in swift 2.2
Try like this:
Timer.scheduledTimer(timeInterval: 0.35, target: self, selector: #selector(createEnemy), userInfo: nil, repeats: true)
You may also used with instance of Timer, if you want to invalidate as per your requirement.
//Create Timer instance
var objTimer = Timer()
//Schedule Timer
self.objTimer = Timer.scheduledTimer(timeInterval: 1.0, target: self, selector: #selector(timerTriggered), userInfo: nil, repeats: true)
//Invalidate Timer after task complete
self.objTimer.invalidate()
I tried
var timer = NSTimer()
timer(timeInterval: 0.01, target: self, selector: update, userInfo: nil, repeats: false)
But, I got an error saying
'(timeInterval: $T1, target: ViewController, selector: () -> (), userInfo: NilType, repeats: Bool) -> $T6' is not identical to 'NSTimer'
This will work:
override func viewDidLoad() {
super.viewDidLoad()
// Swift block syntax (iOS 10+)
let timer = Timer(timeInterval: 0.4, repeats: true) { _ in print("Done!") }
// Swift >=3 selector syntax
let timer = Timer.scheduledTimer(timeInterval: 0.4, target: self, selector: #selector(self.update), userInfo: nil, repeats: true)
// Swift 2.2 selector syntax
let timer = NSTimer.scheduledTimerWithTimeInterval(0.4, target: self, selector: #selector(MyClass.update), userInfo: nil, repeats: true)
// Swift <2.2 selector syntax
let timer = NSTimer.scheduledTimerWithTimeInterval(0.4, target: self, selector: "update", userInfo: nil, repeats: true)
}
// must be internal or public.
#objc func update() {
// Something cool
}
For Swift 4, the method of which you want to get the selector must be exposed to Objective-C, thus #objc attribute must be added to the method declaration.
Repeated event
You can use a timer to do an action multiple times, as seen in the following example. The timer calls a method to update a label every half second.
Here is the code for that:
import UIKit
class ViewController: UIViewController {
var counter = 0
var timer = Timer()
#IBOutlet weak var label: UILabel!
// start timer
#IBAction func startTimerButtonTapped(sender: UIButton) {
timer.invalidate() // just in case this button is tapped multiple times
// start the timer
timer = Timer.scheduledTimer(timeInterval: 0.5, target: self, selector: #selector(timerAction), userInfo: nil, repeats: true)
}
// stop timer
#IBAction func cancelTimerButtonTapped(sender: UIButton) {
timer.invalidate()
}
// called every time interval from the timer
func timerAction() {
counter += 1
label.text = "\(counter)"
}
}
Delayed event
You can also use a timer to schedule a one time event for some time in the future. The main difference from the above example is that you use repeats: false instead of true.
timer = Timer.scheduledTimer(timeInterval: 2.0, target: self, selector: #selector(delayedAction), userInfo: nil, repeats: false)
The above example calls a method named delayedAction two seconds after the timer is set. It is not repeated, but you can still call timer.invalidate() if you need to cancel the event before it ever happens.
Notes
If there is any chance of starting your timer instance multiple times, be sure that you invalidate the old timer instance first. Otherwise you lose the reference to the timer and you can't stop it anymore. (see this Q&A)
Don't use timers when they aren't needed. See the timers section of the Energy Efficiency Guide for iOS Apps.
Related
How to work with dates and time in Swift
Updated to Swift 4, leveraging userInfo:
class TimerSample {
var timer: Timer?
func startTimer() {
timer = Timer.scheduledTimer(timeInterval: 5.0,
target: self,
selector: #selector(eventWith(timer:)),
userInfo: [ "foo" : "bar" ],
repeats: true)
}
// Timer expects #objc selector
#objc func eventWith(timer: Timer!) {
let info = timer.userInfo as Any
print(info)
}
}
As of iOS 10 there is also a new block based Timer factory method which is cleaner than using the selector:
_ = Timer.scheduledTimer(withTimeInterval: 5, repeats: false) { timer in
label.isHidden = true
}
Swift 5
I personally prefer the Timer with the block closure:
Timer.scheduledTimer(withTimeInterval: 1, repeats: false) { (_) in
// TODO: - whatever you want
}
Swift 3, pre iOS 10
func schedule() {
DispatchQueue.main.async {
self.timer = Timer.scheduledTimer(timeInterval: 20, target: self,
selector: #selector(self.timerDidFire(timer:)), userInfo: nil, repeats: false)
}
}
#objc private func timerDidFire(timer: Timer) {
print(timer)
}
Swift 3, iOS 10+
DispatchQueue.main.async {
self.timer = Timer.scheduledTimer(withTimeInterval: 20, repeats: false) { timer in
print(timer)
}
}
Notes
It needs to be on the main queue
Callback function can be public, private, ...
Callback function needs to be #objc
Check with:
Swift 2
var timer = NSTimer.scheduledTimerWithTimeInterval(0.01, target: self, selector: Selector("update"), userInfo: nil, repeats: true)
Swift 3, 4, 5
var timer = Timer.scheduledTimer(timeInterval: 0.01, target: self, selector: #selector(self.update), userInfo: nil, repeats: true)
You will need to use Timer instead of NSTimer in Swift 3.
Here is an example:
Timer.scheduledTimer(timeInterval: 1,
target: self,
selector: #selector(YourController.update),
userInfo: nil,
repeats: true)
// #objc selector expected for Timer
#objc func update() {
// do what should happen when timer triggers an event
}
First declare your timer
var timer: Timer?
Then add line in viewDidLoad() or in any function you want to start the timer
timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(action), userInfo: nil, repeats: false)
This is the func you will callback it to do something it must be #objc
#objc func action () {
print("done")
}
for swift 3 and Xcode 8.2
(nice to have blocks, but if You compile for iOS9 AND want userInfo):
...
self.timer = Timer(fireAt: fire,
interval: deltaT,
target: self,
selector: #selector(timerCallBack(timer:)),
userInfo: ["custom":"data"],
repeats: true)
RunLoop.main.add(self.timer!, forMode: RunLoopMode.commonModes)
self.timer!.fire()
}
func timerCallBack(timer: Timer!){
let info = timer.userInfo
print(info)
}
SimpleTimer (Swift 3.1)
Why?
This is a simple timer class in swift that enables you to:
Local scoped timer
Chainable
One liners
Use regular callbacks
Usage:
SimpleTimer(interval: 3,repeats: true){print("tick")}.start()//Ticks every 3 secs
Code:
class SimpleTimer {/*<--was named Timer, but since swift 3, NSTimer is now Timer*/
typealias Tick = ()->Void
var timer:Timer?
var interval:TimeInterval /*in seconds*/
var repeats:Bool
var tick:Tick
init( interval:TimeInterval, repeats:Bool = false, onTick:#escaping Tick){
self.interval = interval
self.repeats = repeats
self.tick = onTick
}
func start(){
timer = Timer.scheduledTimer(timeInterval: interval, target: self, selector: #selector(update), userInfo: nil, repeats: true)//swift 3 upgrade
}
func stop(){
if(timer != nil){timer!.invalidate()}
}
/**
* This method must be in the public or scope
*/
#objc func update() {
tick()
}
}
timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(createEnemy), userInfo: nil, repeats: true)
And Create Fun By The Name createEnemy
fund createEnemy ()
{
do anything ////
}
In Swift 3 something like this with #objc:
func startTimerForResendingCode() {
let timerIntervalForResendingCode = TimeInterval(60)
Timer.scheduledTimer(timeInterval: timerIntervalForResendingCode,
target: self,
selector: #selector(timerEndedUp),
userInfo: nil,
repeats: false)
}
#objc func timerEndedUp() {
output?.timerHasFinishedAndCodeMayBeResended()
}
If you init method of timer
let timer = Timer(timeInterval: 3, target: self, selector: #selector(update(_:)), userInfo: [key : value], repeats: false)
func update(_ timer : Timer) {
}
then add it to loop using method other selector will not be called
RunLoop.main.add(timer!, forMode: .defaultRunLoopMode)
NOTE : If you are want this to repeat make repeats true and keep the reference of timer otherwise update method will not be called.
If you are using this method.
Timer.scheduledTimer(timeInterval: seconds, target: self, selector: #selector(update(_:)), userInfo: nil, repeats: true)
keep a reference for later use if repeats is true.
I tried to do in a NSObject Class and this worked for me:
DispatchQueue.main.asyncAfter(deadline: .now() + .milliseconds(300)) {
print("Bang!") }
NSTimer has been renamed to Timer in Swift 4.2.
this syntax will work in 4.2:
let timer = Timer.scheduledTimer(timeInterval: 1.0, target: self, selector: #selector(UIMenuController.update), userInfo: nil, repeats: true)