Create a Timer Publisher using Swift Combine
Solution 1
Here you have an example of a Combine timer. I am using a global, but of course you should use whatever is applicable to your scenario (environmentObject, State, etc).
import SwiftUI
import Combine
class MyTimer {
let currentTimePublisher = Timer.TimerPublisher(interval: 1.0, runLoop: .main, mode: .default)
let cancellable: AnyCancellable?
init() {
self.cancellable = currentTimePublisher.connect() as? AnyCancellable
}
deinit {
self.cancellable?.cancel()
}
}
let timer = MyTimer()
struct Clock : View {
@State private var currentTime: Date = Date()
var body: some View {
VStack {
Text("\(currentTime)")
}
.onReceive(timer.currentTimePublisher) { newCurrentTime in
self.currentTime = newCurrentTime
}
}
}
Solution 2
Using ObservableObject
to Create a Timer Publisher using Swift Combine
class TimeCounter: ObservableObject {
@Published var time = 0
lazy var timer = Timer.scheduledTimer(withTimeInterval: 1, repeats: true) { _ in self.time += 1 }
init() { timer.fire() }
}
That's it! now you just need to observe for changes:
struct ContentView: View {
@StateObject var timeCounter = TimeCounter()
var body: some View {
Text("\(timeCounter.time)")
}
}
Solution 3
I implemented a Combine timer with a new feature allowing you to switch between different intervals.
class CombineTimer {
private let intervalSubject: CurrentValueSubject<TimeInterval, Never>
var interval: TimeInterval {
get {
intervalSubject.value
}
set {
intervalSubject.send(newValue)
}
}
var publisher: AnyPublisher<Date, Never> {
intervalSubject
.map {
Timer.TimerPublisher(interval: $0, runLoop: .main, mode: .default).autoconnect()
}
.switchToLatest()
.eraseToAnyPublisher()
}
init(interval: TimeInterval = 1.0) {
intervalSubject = CurrentValueSubject<TimeInterval, Never>(interval)
}
}
To start the timer, simply subscribe to the publisher
property.
SomeView()
.onReceive(combineTimer.publisher) { date in
// ...
}
You can switch to a new timer with a different interval by changing the interval
property.
combineTimer.interval = someNewInterval
eivindml
Love to create stuff. Mostly with code. Especially for Apple products. The 🦊 is my spirit animal.
Updated on June 06, 2022Comments
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eivindml almost 2 years
I've been watching the Data Flow Through SwiftUI WWDC talk. They have a slide with a sample code where they use a Timer publisher that gets connected to a SwiftUI View, and updates the UI with the time.
I'm working on some code where I want to do the exact same thing, but can't figure out how this
PodcastPlayer.currentTimePublisher
is implemented, and then hooked to the UI struct. I have also watched all the videos about Combine.How can I achieve this?
The sample code:
struct PlayerView : View { let episode: Episode @State private var isPlaying: Bool = true @State private var currentTime: TimeInterval = 0.0 var body: some View { VStack { // ... Text("\(playhead, formatter: currentTimeFormatter)") } .onReceive(PodcastPlayer.currentTimePublisher) { newCurrentTime in self.currentTime = newCurrentTime } } }
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eivindml almost 5 yearsAwesome, thank you. So I guess in the example they have the
currentTimePublisher
as a static class variable. -
kontiki almost 5 yearsIt looks like it. I haven't look at that exercise in detail. My posted answer is just one way to create a timer with Combine. Maybe there are others...
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eivindml almost 5 yearsYes. And it works great. Just makes sense to have it as a static variable for them and my case, since it should ever only exist one timer.
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WikipediaBrown over 3 yearsWhat is the difference between this and
Timer.TimerPublisher(interval: 1.0, runLoop: .main, mode: .default)
? -
Roland Lariotte over 3 yearsHow would you cancel your CombineTimer?
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zdravko zdravkin over 3 yearsI think deinit don't need, as cancel() is called automatically when you deinit