swift-composable-architecture-mirror/Examples/CaseStudies/SwiftUICaseStudies/03-Effects-Timers.swift

import ComposableArchitecture
import SwiftUI

private let readMe = """
  This application demonstrates how to work with timers in the Composable Architecture.

  It makes use of the `.timer` method on clocks, which is a helper provided by the Swift Clocks \
  library included with this library. The helper provides an `AsyncSequence`-friendly API for \
  dealing with times in asynchronous code.
  """

@Reducer
struct Timers {
  @ObservableState
  struct State: Equatable {
    var isTimerActive = false
    var secondsElapsed = 0
  }

  enum Action {
    case onDisappear
    case timerTicked
    case toggleTimerButtonTapped
  }

  @Dependency(\.continuousClock) var clock
  private enum CancelID { case timer }

  var body: some Reducer<State, Action> {
    Reduce { state, action in
      switch action {
      case .onDisappear:
        return .cancel(id: CancelID.timer)

      case .timerTicked:
        state.secondsElapsed += 1
        return .none

      case .toggleTimerButtonTapped:
        state.isTimerActive.toggle()
        return .run { [isTimerActive = state.isTimerActive] send in
          guard isTimerActive else { return }
          for await _ in self.clock.timer(interval: .seconds(1)) {
            await send(.timerTicked, animation: .interpolatingSpring(stiffness: 3000, damping: 40))
          }
        }
        .cancellable(id: CancelID.timer, cancelInFlight: true)
      }
    }
  }
}

struct TimersView: View {
  var store: StoreOf<Timers>

  var body: some View {
    Form {
      AboutView(readMe: readMe)

      ZStack {
        Circle()
          .fill(
            AngularGradient(
              gradient: Gradient(
                colors: [
                  .blue.opacity(0.3),
                  .blue,
                  .blue,
                  .green,
                  .green,
                  .yellow,
                  .yellow,
                  .red,
                  .red,
                  .purple,
                  .purple,
                  .purple.opacity(0.3),
                ]
              ),
              center: .center
            )
          )
          .rotationEffect(.degrees(-90))
        GeometryReader { proxy in
          Path { path in
            path.move(to: CGPoint(x: proxy.size.width / 2, y: proxy.size.height / 2))
            path.addLine(to: CGPoint(x: proxy.size.width / 2, y: 0))
          }
          .stroke(.primary, lineWidth: 3)
          .rotationEffect(.degrees(Double(store.secondsElapsed) * 360 / 60))
        }
      }
      .aspectRatio(1, contentMode: .fit)
      .frame(maxWidth: 280)
      .frame(maxWidth: .infinity)
      .padding(.vertical, 16)

      Button {
        store.send(.toggleTimerButtonTapped)
      } label: {
        Text(store.isTimerActive ? "Stop" : "Start")
          .padding(8)
      }
      .frame(maxWidth: .infinity)
      .tint(store.isTimerActive ? Color.red : .accentColor)
      .buttonStyle(.borderedProminent)
    }
    .navigationTitle("Timers")
    .onDisappear {
      store.send(.onDisappear)
    }
  }
}

#Preview {
  NavigationStack {
    TimersView(
      store: Store(initialState: Timers.State()) {
        Timers()
      }
    )
  }
}