Swift Observation framework and debounce

Question

I am currently migrating some SwiftUI code from combine to the new observation framework and I want to know how I can I maintain debounce? Is there anyway to natively debounce from within the Observation framework?

I have tried combining Combine ~no pun intended~ with the Observation framework and it produces a slew of errors.

Answer 1

No, there is no debounce because the Observer mechanism is designed for the synchronous delivery of information.

Debouncing involves a delay and therefore, by its very nature, is concerned with the asynchronous delivery of information. As such, debounce would be out-of-place in the Observer mechanism.

Combine is for handling asynchronous messages and debounce is appropriate in that system.

Answer 2

Usually you don't need debounce in SwiftUI because all state changes are debounced already, that is you can set the state many times but body will only be called once afterwards. Combine's ObservableObject matches this behaviour by sending objectWillChange to SwiftUI instead of didChange which would be too late for debouncing.

However if you really need debounce, e.g. for your model or networking layers, then there is a debounce in the AsyncAlgorithms Swift package here.

In Xcode choose File->Add Package Depdendencies and choose AsyncAlgorithms.

Answer 3

If you just want to debounce, you can use this code :

public actor Debouncer {
    private let duration: Duration
    private var isPending = false
    
    public init(duration: Duration) {
        self.duration = duration
    }
    
    public func sleep() async -> Bool {
        if isPending { return false }
        isPending = true
        try? await Task.sleep(for: duration)
        isPending = false
        return true
    }
}

Put this code in your Observable:

    private let debouncer = Debouncer(duration: .seconds(0.5))

    func checkEmailValidity() async {
        guard await debouncer.sleep() else { return }
        
        ... do your debounced stuff here ...
    }

And somewhere on your SwiftUI View for example:

    .onChange(of: viewModel.email) { Task { await viewModel.checkEmailValidity() } }