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- Download this app from Microsoft Store for Windows 10, Windows 8.1. See screenshots, read the latest customer reviews, and compare ratings for Countdown-Timer.
- Defaults write com.apple.dock autohide-delay -int 0 defaults write com.apple.dock autohide-time-modifier -float 0.4 killall Dock You can change the values for 0 and 0.4 to see if a different setting works better for you. Don't forget to change int to float if you want to use a float instead of 0.
- The window will then float above all other apps on your computer, whether it be your web browser, photo-editing tool, music player, etc. To play videos from Netflix, you'll need to have Microsoft's Silverlight downloaded from Safari (which it ditched for HTML5 last year), if you don't already.
Timers are super handy in Swift, from creating repeating tasks to scheduling work with a delay. This tutorial explains how to create a timer in Swift.
We’ll discuss how to use the
Timer
class, formerly known as NSTimer
, to schedule timers. We’ll get into repeating and non-repeating timers, using run loops, keeping track of timers, and how you can reduce their energy and power impact.Ready? Let’s go.
How To Create a Repeating Timer with Swift
Creating a repeating timer in Swift is surprisingly simple. Here’s how:
In the above code, a few things happen:
- A timer is created using the
Timer.scheduledTimer(..)
class method. Its return value is assigned to the constanttimer
. This constant now contains a reference to the timer, which will come in handy later on. - The parameters of
scheduledTimer()
are the timer interval of 1 second, which uses a mechanism known as target-action, someuserInfo
that’s set tonil
, and the parameterrepeats
set totrue
. - We’ve also coded a function
fire()
. This is the function that’s called when the timer fires, i.e. roughly every second. By settingtarget
toself
andselector
to#selector(fire)
you’re indicating that whenever the timer fires, the functionfire()
ofself
needs to be called.
The above code should run in a class context, for instance in a view controller class. The
fire()
function is part of the class, and self
refers to the current class instance.You can also create a timer using a closure. Like this:
In the above code, the last parameter
block
takes a closure. The closure has one parameter, the timer
itself.The timer with target-action and
self
won’t work in an Xcode playground, unless you create a class or struct. Here’s the code you can use to create a timer in a playground in Xcode:In the above code, we’re setting
needsIndefiniteExecution
to true
so the playground won’t automatically stop running when the playground is finished. The timer is able to fire this way, and at that point we call finishExecution()
to halt the playground.Thanks to trailing-closure syntax we can make that closure-based timer even more concise. Like this:
See how the last argument label is omitted? That’s because the last parameter is a closure. It makes the code more concise. Neat! How to find dates on deleted apps.
The attribute makes the
fire()
function available in Objective-C. The Timer
class is part of the Objective-C runtime, so that’s why we need that attribute.Learn how to build iOS apps
Get started with iOS 14 and Swift 5
Sign up for my iOS development course, and learn how to build great iOS 14 apps with Swift 5 and Xcode 12.
Managing Timers and Non-Repeating Timers
In the previous example, we’ve used 5 parameters to create a timer. They are:
timeInterval
: the interval between timer fires in seconds, its type isDouble
target
: a class instance that the function forselector
should be called on, oftenself
selector
: the function to call when the timer fires, with#selector(..)
userInfo
: a dictionary with data that’s provided to theselector
, ornil
repeats
: whether this timer is repeating or non-repeating
Creating a non-repeating timer is as simple as setting the
repeats
parameter to false
. The timer will only fire once and immediately invalidate itself after.Then how do you stop a repeating timer? It’s simple. Here’s how:
You’d keep track of the
timer
variable somewhere, for instance through a stored property on the class that you’re using the timer in. You can then use that property to manage the timer.You can also attach some extra information to a timer by using
userInfo
. This value is sent to the function that fires, via its timer
parameter. Here’s an example:In the above code, we’ve added the dictionary
['score': 10]
to the timer. When it fires, this dictionary is passed to the fire(timer:)
function as timer.userInfo
. Inside the fire(timer:)
function we’re checking if the userInfo
property has the type we expect, and we get the right value.Let’s look at a practical example for using timers, next.
Creating A Countdown Timer
Imagine you’re creating a game. The user has 60 seconds to solve a puzzle and score points. As the count down timer runs out, you’re keeping track of how many seconds are left.
First, we’re creating two properties at the top of our game class. Something like:
The timer doesn’t start immediately. Until it starts, the
timer
property is nil. At some point the game has started, so we also start the timer:The timer calls
onTimerFires()
every second, indefinitely. And here’s that function:Every time the timer fires it subtracts 1 from
timeLeft
, and it updates the “time left” label. When the timer reaches zero, timer
is invalidated and set to nil
.This will effectively create a countdown timer that counts down from 60 to zero. And at a point in the future, you can of course reset the countdown and start again.
Timers, Runloops and Tolerance
Timers work in conjunction with run loops. Run loops are a fundamental part of threads and concurrency.
It’s easiest to imagine run loops like a ferris wheel. People can enter a passenger car and get moved around by the wheel. In a similar way, you can schedule a task on a run loop. The run loop keeps “looping” and executing tasks. When there are no tasks to execute, the run loop waits or quits.
The way run loops and timers work together, is that the run loop checks if a timer should fire. A timer isn’t a real-time mechanism, because the firing of the timer can coincide with the runloop already executing another task. You can compare this to wanting to enter the ferris wheel when there’s no car yet at the bottom entrance. The result is that a timer can fire later than it’s scheduled.
This isn’t necessarily a bad thing. Don’t forget you’re running code on a mobile device that has energy and power constraints! The device can schedule run loops more efficiently to save power.
You can also help the system save power by using a timer property called
tolerance
. This will tell the scheduling system: “Look, I want this to run every second, but I don’t care if it’s 0.2 seconds too late.” This of course depends on your app. Apple recommends to set the tolerance
to at least 10% of the interval time for a repeating timer.Here’s an example:
The
tolerance
property uses the same units as the timeInterval
property, so the above code will use a tolerance of 200 milliseconds.The tolerance will never cause a timer to fire early, only later. And the tolerance will neither cause a timer to “drift”, i.e. when one timer fire is too late, it won’t affect the scheduled time of the next timer fire.
When using the
Timer.scheduledTimer(..)
class method, the timer is automatically scheduled on the current run loop in the default mode. This is typically the run loop of the main thread. As a result, timers may not fire when the run loop on the main thread is busy, for example when the user of your app is interacting with the UI.You can solve this by manually scheduling the timer on a run loop yourself. Here’s how:
The first line of code will create an instance of
Timer
using the Timer(..)
initializer. The second line of code adds the timer to the current run loop using the .commonModes
input mode. In short, this tells the run loop that the timer should be checked for all “common” input modes, which effectively lets the timer fire during the interaction with UI.By the way, a common source for frustration is accidentally using the
Timer(..)
initializer when you wanted to use the Timer.scheduledTimer(..)
to create a timer. If you use the former, the timer won’t fire until you’ve added it to a run loop! And you’ll pull your hair out, because you’re certain you’ve scheduled the timer correctly…Executing Code with a Delay
A common scenario in practical iOS development is executing some code with a small delay. It’s easiest to use Grand Central Dispatch for that purpose, and not use a
Timer
.The following code executes a task on the main thread with a 300 millisecond delay:
It’s more concise than using
Timer
. And because you’re only running it once, there’s no need to keep track of a timer anyway.Learn how to build iOS apps
Get started with iOS 14 and Swift 5
Sign up for my iOS development course, and learn how to build great iOS 14 apps with Swift 5 and Xcode 12.
Further Reading
![Download Download](/uploads/1/3/4/1/134199901/771995167.png)
So, now you know! When you need your code run in a timely manner,
Timer
is a tool you can depend on. Give or take ;-)Want to learn more? Check out these resources:
Timers are super handy in Swift, from creating repeating tasks to scheduling work with a delay. This tutorial explains how to create a timer in Swift.
We’ll discuss how to use the
Timer
class, formerly known as NSTimer
, to schedule timers. We’ll get into repeating and non-repeating timers, using run loops, keeping track of timers, and how you can reduce their energy and power impact.Ready? Let’s go.
How To Create a Repeating Timer with Swift
Mac app that deletes duplicates gemini. Creating a repeating timer in Swift is surprisingly simple. Here’s how:
In the above code, a few things happen:
- A timer is created using the
Timer.scheduledTimer(..)
class method. Its return value is assigned to the constanttimer
. This constant now contains a reference to the timer, which will come in handy later on. - The parameters of
scheduledTimer()
are the timer interval of 1 second, which uses a mechanism known as target-action, someuserInfo
that’s set tonil
, and the parameterrepeats
set totrue
. - We’ve also coded a function
fire()
. This is the function that’s called when the timer fires, i.e. roughly every second. By settingtarget
toself
andselector
to#selector(fire)
you’re indicating that whenever the timer fires, the functionfire()
ofself
needs to be called.
The above code should run in a class context, for instance in a view controller class. The
fire()
function is part of the class, and self
refers to the current class instance.You can also create a timer using a closure. Like this:
In the above code, the last parameter
block
takes a closure. The closure has one parameter, the timer
itself.The timer with target-action and
self
won’t work in an Xcode playground, unless you create a class or struct. Here’s the code you can use to create a timer in a playground in Xcode:In the above code, we’re setting
needsIndefiniteExecution
to true
so the playground won’t automatically stop running when the playground is finished. The timer is able to fire this way, and at that point we call finishExecution()
to halt the playground.Thanks to trailing-closure syntax we can make that closure-based timer even more concise. Like this: Macos best mail app.
See how the last argument label is omitted? That’s because the last parameter is a closure. It makes the code more concise. Neat!
The attribute makes the
fire()
function available in Objective-C. The Timer
class is part of the Objective-C runtime, so that’s why we need that attribute.Learn how to build iOS apps
Get started with iOS 14 and Swift 5
Sign up for my iOS development course, and learn how to build great iOS 14 apps with Swift 5 and Xcode 12.
Managing Timers and Non-Repeating Timers
In the previous example, we’ve used 5 parameters to create a timer. They are:
timeInterval
: the interval between timer fires in seconds, its type isDouble
target
: a class instance that the function forselector
should be called on, oftenself
selector
: the function to call when the timer fires, with#selector(..)
userInfo
: a dictionary with data that’s provided to theselector
, ornil
repeats
: whether this timer is repeating or non-repeating
Creating a non-repeating timer is as simple as setting the
repeats
parameter to false
. The timer will only fire once and immediately invalidate itself after.Then how do you stop a repeating timer? It’s simple. Here’s how:
You’d keep track of the
timer
variable somewhere, for instance through a stored property on the class that you’re using the timer in. You can then use that property to manage the timer.You can also attach some extra information to a timer by using
userInfo
. This value is sent to the function that fires, via its timer
parameter. Here’s an example:In the above code, we’ve added the dictionary
['score': 10]
to the timer. When it fires, this dictionary is passed to the fire(timer:)
function as timer.userInfo
. Inside the fire(timer:)
function we’re checking if the userInfo
property has the type we expect, and we get the right value.Let’s look at a practical example for using timers, next.
Creating A Countdown Timer
Imagine you’re creating a game. The user has 60 seconds to solve a puzzle and score points. As the count down timer runs out, you’re keeping track of how many seconds are left.
First, we’re creating two properties at the top of our game class. Something like:
https://qqbbzj.weebly.com/mysound-app-for-mac.html. The timer doesn’t start immediately. Until it starts, the
timer
property is nil. At some point the game has started, so we also start the timer:The timer calls
onTimerFires()
every second, indefinitely. And here’s that function:Every time the timer fires it subtracts 1 from
timeLeft
, and it updates the “time left” label. When the timer reaches zero, timer
is invalidated and set to nil
.This will effectively create a countdown timer that counts down from 60 to zero. And at a point in the future, you can of course reset the countdown and start again.
Timers, Runloops and Tolerance
Timers work in conjunction with run loops. Run loops are a fundamental part of threads and concurrency.
It’s easiest to imagine run loops like a ferris wheel. People can enter a passenger car and get moved around by the wheel. In a similar way, you can schedule a task on a run loop. The run loop keeps “looping” and executing tasks. When there are no tasks to execute, the run loop waits or quits.
Timer On Mac
The way run loops and timers work together, is that the run loop checks if a timer should fire. A timer isn’t a real-time mechanism, because the firing of the timer can coincide with the runloop already executing another task. You can compare this to wanting to enter the ferris wheel when there’s no car yet at the bottom entrance. The result is that a timer can fire later than it’s scheduled.
This isn’t necessarily a bad thing. Don’t forget you’re running code on a mobile device that has energy and power constraints! The device can schedule run loops more efficiently to save power.
You can also help the system save power by using a timer property called
tolerance
. This will tell the scheduling system: “Look, I want this to run every second, but I don’t care if it’s 0.2 seconds too late.” This of course depends on your app. Apple recommends to set the tolerance
to at least 10% of the interval time for a repeating timer.Here’s an example:
The
tolerance
property uses the same units as the timeInterval
property, so the above code will use a tolerance of 200 milliseconds.The tolerance will never cause a timer to fire early, only later. And the tolerance will neither cause a timer to “drift”, i.e. when one timer fire is too late, it won’t affect the scheduled time of the next timer fire.
When using the
Timer.scheduledTimer(..)
class method, the timer is automatically scheduled on the current run loop in the default mode. This is typically the run loop of the main thread. As a result, timers may not fire when the run loop on the main thread is busy, for example when the user of your app is interacting with the UI.You can solve this by manually scheduling the timer on a run loop yourself. Here’s how:
The first line of code will create an instance of
Timer
using the Timer(..)
initializer. The second line of code adds the timer to the current run loop using the .commonModes
input mode. In short, this tells the run loop that the timer should be checked for all “common” input modes, which effectively lets the timer fire during the interaction with UI.By the way, a common source for frustration is accidentally using the
Timer(..)
initializer when you wanted to use the Timer.scheduledTimer(..)
to create a timer. If you use the former, the timer won’t fire until you’ve added it to a run loop! And you’ll pull your hair out, because you’re certain you’ve scheduled the timer correctly…Executing Code with a Delay
Free Timer For Mac
A common scenario in practical iOS development is executing some code with a small delay. It’s easiest to use Grand Central Dispatch for that purpose, and not use a
Timer
.The following code executes a task on the main thread with a 300 millisecond delay:
It’s more concise than using
Timer
. And because you’re only running it once, there’s no need to keep track of a timer anyway.Learn how to build iOS apps
Timer Apps For Computer
Get started with iOS 14 and Swift 5
Sign up for my iOS development course, and learn how to build great iOS 14 apps with Swift 5 and Xcode 12.
Further Reading
So, now you know! When you need your code run in a timely manner,
Timer
is a tool you can depend on. Give or take ;-)Want to learn more? Check out these resources: