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December 1, 2022 00:16
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Actor / AsyncStream を使ったカウントダウン的な（とくに意味はない）
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| import SwiftUI | |
| import Combine | |
| struct ContentView: View { | |
| @State var id: Int = 0 | |
| var body: some View { | |
| VStack { | |
| CounterView(from: 10).id(id) | |
| Button("RESET") { id += 1 } | |
| } | |
| } | |
| } | |
| struct CounterView: View { | |
| @StateObject private var viewModel: CounterViewModel | |
| init(from: Int) { | |
| _viewModel = .init(wrappedValue: .init(from: from)) | |
| } | |
| var body: some View { | |
| VStack { | |
| Text("\(viewModel.count)") | |
| .font(.largeTitle) | |
| } | |
| } | |
| } | |
| @MainActor | |
| final class CounterViewModel: ObservableObject { | |
| private let countdownTimer: CountdownModel | |
| private var cancellables = Set<AnyCancellable>() | |
| @Published var count: Int | |
| init(from: Int) { | |
| _count = .init(initialValue: from) | |
| countdownTimer = .init(from: from) | |
| Task { [weak self] in | |
| guard let countSequence = await self?.countdownTimer.count else { return } | |
| for await count in countSequence { | |
| self?.count = count | |
| } | |
| } | |
| .store(in: &cancellables) | |
| } | |
| deinit { print("🧹 CounterViewModel") } | |
| } | |
| actor CountdownModel { | |
| private let countSubject = PassthroughSubject<Int, Never>() | |
| private let from: Int | |
| private var countTask: Task<Void, Never>? | |
| private var cancellables: Set<AnyCancellable> = [] | |
| lazy var count = AsyncStream<Int> { continuation in | |
| countSubject | |
| .sink { count in | |
| continuation.yield(count) | |
| } | |
| .store(in: &cancellables) | |
| continuation.onTermination = { _ in | |
| Task { await self.onTermination() } | |
| } | |
| } | |
| init(from: Int) { | |
| self.from = from | |
| Task { await start() } | |
| } | |
| func start() { | |
| countTask = Task { | |
| for n in (0...from).reversed() { | |
| countSubject.send(n) | |
| try? await Task.sleep(nanoseconds: 1_000_000_000) | |
| } | |
| } | |
| } | |
| func onTermination() { | |
| countTask?.cancel() | |
| } | |
| deinit { print("🧹 CountdownModel") } | |
| } | |
| extension Task { | |
| func store(in cancellables: inout Set<AnyCancellable>) { | |
| AnyCancellable { self.cancel() }.store(in: &cancellables) | |
| } | |
| private func asCancellable() -> AnyCancellable { | |
| .init { self.cancel() } | |
| } | |
| } |
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メモリ回収の流れ（想定）：