swift-composable-architecture-mirror/Sources/ComposableArchitecture/Effects/Timer.swift

import Combine
import CombineSchedulers

extension Effect where Failure == Never {
  /// Returns an effect that repeatedly emits the current time of the given
  /// scheduler on the given interval.
  ///
  /// This effect serves as a testable alternative to `Timer.publish`, which
  /// performs its work on a run loop, _not_ a scheduler.
  ///
  ///     struct TimerId: Hashable {}
  ///
  ///     switch action {
  ///     case .startTimer:
  ///       return Effect.timer(id: TimerId(), every: 1, on: environment.scheduler)
  ///         .map { .timerUpdated($0) }
  ///     case let .timerUpdated(date):
  ///       state.date = date
  ///       return .none
  ///     case .stopTimer:
  ///       return .cancel(id: TimerId())
  ///
  /// - Parameters:
  ///   - interval: The time interval on which to publish events. For example, a value of `0.5`
  ///     publishes an event approximately every half-second.
  ///   - scheduler: The scheduler on which the timer runs.
  ///   - tolerance: The allowed timing variance when emitting events. Defaults to `nil`, which
  ///     allows any variance.
  ///   - options: Scheduler options passed to the timer. Defaults to `nil`.
  public static func timer<S>(
    id: AnyHashable,
    every interval: S.SchedulerTimeType.Stride,
    tolerance: S.SchedulerTimeType.Stride? = nil,
    on scheduler: S,
    options: S.SchedulerOptions? = nil
  ) -> Effect where S: Scheduler, S.SchedulerTimeType == Output {

    Publishers.Timer(every: interval, tolerance: tolerance, scheduler: scheduler, options: options)
      .autoconnect()
      .setFailureType(to: Failure.self)
      .eraseToEffect()
      .cancellable(id: id)
  }
}