.task{}のバックポート検討

ContentView.swift

import SwiftUI

func longlongAsyncFunction() async {
    let id = UUID()
    print("\(id): start")
    do {
        try await withTaskCancellationHandler {
            try await Task.sleep(nanoseconds: 1000 * 1000 * 1000 * 10)
            print("\(id): end")
        } onCancel: {
            print("\(id): cancel")
        }
    } catch {
        print("\(error)")
    }
}

struct CountView: View {
    @State var count = 0
    var body: some View {
        VStack {
            Text("Hello \(count)")
            Button("Tap") {
                count += 1
            }
        }
        .task2 {
            await longlongAsyncFunction()
        }
//        .modifier(TaskModifier {
//            await longlongAsyncFunction()
//        })
    }
}

struct ContentView: View {
    @State var count = 0
    var body: some View {
        NavigationView {
            NavigationLink("Next") {
                CountView()
            }
        }
    }
}

public extension View {
  func task2(
    priority: TaskPriority = .userInitiated,
    _ action: @escaping @Sendable () async -> ()
  ) -> some View {
    var task: Task<(), Never>?
    return onAppear {
      task = Task(priority: priority, operation: action)
    }
    .onDisappear {
      task?.cancel()
    }
  }
}

struct TaskModifier: ViewModifier {
    var action: @Sendable () async -> ()
    @State var task: Task<(), Never>?

    func body(content: Content) -> some View {
        return content.onAppear {
          task = Task(operation: action)
        }
        .onDisappear {
          task?.cancel()
        }
    }
}

extension UUID: @unchecked Sendable {}