Repeat: modern NSTimer in GCD

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Repeat is small lightweight alternative to NSTimer with a modern Swift Syntax, no strong references, multiple observers reusable instances. Repeat is based upon GCD - Grand Central Dispatch.

› Learn More: If you want to learn more about it check out my article on Medium.

Main features offered by Repeat are:

• Simple, less verbose APIs methods to create and manage our timer. Just call every() or once to create a new Timer even in background thread.
• Avoid strong reference to the destination target and avoid NSObject inheritance.
• Support multiple observers to receive fire events from timer.
• Ability to pause , start , resume and reset our timer without allocating a new instance.
• Ability to set different repeat modes (infinite : infinite sequence of fires, at regular intervals, finite : a finite sequence of fires, at regular intervals, once : a single fire events at specified interval since start).

Examples

Create single fire timer

The following code create a timer which fires a single time after 5 seconds.

Repeat.once(after: .seconds(5)) { timer in
  // do something	
}

Create recurrent finite timer

The following code create a recurrent timer: it will fire every 10 minutes for 5 times, then stops.

Repeat.every(.minutes(10), count: 5) { timer  in
  // do something		
}

Create recurrent infinite timer

The following code create a recurrent timer which fires every hour until it is manually stopped .

Repeat.every(.hours(1)) { timer in
  // do something
}

Manage a timer

You can create a new instance of timer and start as needed by calling the start() function.

let timer = Repeat(interval: .seconds(5), mode: .infinite) { _ in
	// do something		
}
timer.start()

Other functions are:

• start(): start a paused or newly created timer
• pause(): pause a running timer
• reset(_ interval: Interval, restart: Bool): reset a running timer, change the interval and restart again if set.
• fire(): manually fire an event of the timer from an external source

Properties:

• .id: unique identifier of the timer
• .mode: define the type of timer (infinite,finite,once)
• .remainingIterations: for a .finite mode it contains the remaining number of iterations before it finishes.

Adding/Removing Observers

By default a new timer has a single observer specified by the init functions. You can, however, create additional observer by using observe() function. The result of this call is a token identifier you can use to remove the observer in a second time. Timer instance received in callback is weak.

let token = timer.observe { _ in
	// a new observer is called		
}
timer.start()

You can remove an observer by using the token:

timer.remove(token)

Observing state change

Each timer can be in one of the following states, you can observe via .state property:

• .paused: timer is in idle (never started yet) or paused
• .running: timer is currently active and running
• .finished: timer lifecycle is finished (it's valid for a finite/once state timer)

You can listen for state change by assigning a function callback for .onStateChanged property.

timer.onStateChanged = { (timer,newState) in
	// your own code
}

Requirements

Repeat is compatible with Swift 4.x. All Apple platforms are supported:

• iOS 8.0+
• macOS 10.9+
• watchOS 2.0+
• tvOS 9.0+

Latest Version

Latest version of Repeat is 0.2.0 published on 2018/03/04.

Changelog - 0.2.0:

• #1: Fixed CocoaPods installation
• #2: Fixed leaks with GCD while deallocating dispatch queue
• #3: Refactoring timer's state using a State enum which define the possible states of the timer (paused,running or finished).

Installation

Install via CocoaPods

CocoaPods is a dependency manager for Objective-C, which automates and simplifies the process of using 3rd-party libraries like Repeat in your projects. You can install it with the following command:

$ gem install cocoapods

CocoaPods 1.0.1+ is required to build Repeat.

Install via Podfile

To integrate Repeat into your Xcode project using CocoaPods, specify it in your Podfile:

source 'https://github.com/CocoaPods/Specs.git'
platform :ios, '8.0'

target 'TargetName' do
use_frameworks!
pod 'Repeat'
end

Then, run the following command:

$ pod install

Carthage

Carthage is a decentralized dependency manager that builds your dependencies and provides you with binary frameworks.

You can install Carthage with Homebrew using the following command:

$ brew update
$ brew install carthage

To integrate Repeat into your Xcode project using Carthage, specify it in your Cartfile:

github "malcommac/Repeat"

Run carthage to build the framework and drag the built Repeat.framework into your Xcode project.