PTTimer is a Swift class that can be used to create timers that accurately track time.

PTTimer is an project that I originally created for an iOS app I've been working on. I decided to extract it from my app and open-source it because I noticed that there wasn't really a good resource for Swift stopwatch/countdown timers available.

I was seeing blog posts that suggested using a simple counter to build the timer. This meant doing the following:

DO NOT DO THIS!!!

let seconds = 60
let timer = Timer.scheduledTimer(timeInterval: 1.0, target: self,
                                selector: #selector(timerRunning),
                                userInfo: nil, repeats: true)

func timerRunning() {
  second -= 1
}

This is a very bad idea (as I learned the hard way) because Swift's Timer doesn't fire when the app is in the background. Therefore, when you return from the background and the Timer fires again, it starts off where it left. If the app was in the background for 30 seconds, your timer doesn't correct for that at all. This is a sure-fire way to get an inaccurate timer. What's the point then??

PTTimer uses Timer underneath, but the advantage of PTTimer is that it manages the timer clock for you. I found the best way to deal with app backgrounding was to use the system clock to manage the timer, which allows for self-correction when on the next Timer even is fired.

• No dependencies!
• Comes with two built-in timers:
  • a CountUp timer (starts at 0 and counts up)
  • a CountDown timer (starts at however many seconds you specify and counts down to 0)
• Continues keeping time even when your app is in the background
• Accurately counts time based on the device clock
• Subclass-able: Override methods on PTTimer to completely customize your timer.

PTTimer is available through CocoaPods. To install it, simply add the following line to your Podfile:

pod 'PTTimer'

First, be sure to import PTTimer

// This creates a countdown timer that begins at 5 minutes
let timer = PTTimer.Down(initialTime: 60 * 5)

• (default 90*60 or 90 minutes)

let timer = PTTimer.Up()
// customize the maxSeconds
let timer = PTTimer.Up(maxSeconds: 60 * 15)

// start the timer
timer.start()

// pause the timers
timer.pause()

// reset the timer back to the original state
// (0 if count up, initialTime if count down)
timer.reset()

// read the state of the timer (.paused, .running, .reset)
let state = timer.state

// read the current seconds of the timer
let currentSeconds = timer.seconds()

Feel free to create your own timer by subclassing PTTimer

Utilize the delegate to take actions when the timer state changes and when the timer's time changes

func timerTimeDidChange(seconds: Int) {
  // Update labels, buttons when the timer seconds have changed
  // consider a formatter to turn seconds into 00:00 or similar
}

func timerDidPause() {
  // update label colors, buttons for a paused timer
}

func timerDidStart() {
  // update label colors, buttons for a started timer
}

func timerDidReset() {
  // update label colors, buttons now that the timer has been reset
}

Check out the ExampleTimer app for an example usage of PTTimer

From ExampleTimer directory, run pod install.

In XCode, open ExampleTimer/ExampleTimer.xcworkspace and run.

You can see UI code for the timer in ExampleTimer/ExampleTimer/ViewController.swift

Contributions are welcomed and encouraged! Anything that you believe will better this project, I'd love to hear. I reserve the right to accept or deny changes at my discretion.

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create pull request

GitHub Issues is for reporting bugs, discussing features and general feedback in PTTimer. Be sure to check our past issues before opening any new issues.

If you are posting about a crash in your application, a stack trace is helpful, but additional context, in the form of code and explanation, is necessary to be of any use.

PTTimer is available under the MIT license. See the LICENSE file for more info.