AsyncChanges

AsyncChanges.swift

import SwiftUI
import AsyncAlgorithms

struct AsyncChanges<V>: ViewModifier where V : Equatable, V: Sendable {
    typealias Element = (oldValue: V, newValue: V)
    typealias Action = (AsyncStream<Element>) async -> Void

    @State private var streamPair = AsyncStream<Element>.makeStream()
    private let action: Action
    private let value: V

    init(of value: V, initial: Bool, action: @escaping Action) {
        self.action = action
        self.value = value
    }

    func body(content: Content) -> some View {
        content
            .onChange(of: value, initial: true) { oldValue, newValue in
                streamPair.continuation.yield((oldValue, newValue))
            }
            .task {
                await action(streamPair.stream)
            }
    }
}

extension View {
	public func asyncChanges<V>(
		of value: V,
		initial: Bool = false,
		action: @escaping (AsyncStream<(oldValue: V, newValue: V)>) async -> Void
	) -> some View where V: Equatable, V: Sendable {
		modifier(AsyncChanges<V>(of: value, initial: initial, action: action))
	}
}

struct ContentView: View {
	@State private var username = ""

    var body: some View {
		TextField("Username", text: self.$username)
			.asyncChanges(of: username) { sequence in
				for await value in sequence.debounce(for: .seconds(0.25)) {
					print("debounced value: \(value.newValue)")
				}
			}
    }
}