swift-composable-architecture-mirror/Sources/ComposableArchitecture/SwiftUI/Alert.swift

import SwiftUI

extension View {
  /// Displays an alert when then store's state becomes non-`nil`, and dismisses it when it becomes
  /// `nil`.
  ///
  /// - Parameters:
  ///   - store: A store that describes if the alert is shown or dismissed.
  ///   - dismissal: An action to send when the alert is dismissed through non-user actions, such
  ///     as when an alert is automatically dismissed by the system. Use this action to `nil` out
  ///     the associated alert state.
  @ViewBuilder public func alert<Action>(
    _ store: Store<AlertState<Action>?, Action>,
    dismiss: Action
  ) -> some View {
    if #available(iOS 15, macOS 12, tvOS 15, watchOS 8, *) {
      self.modifier(
        NewAlertModifier(
          viewStore: ViewStore(store, removeDuplicates: { $0?.id == $1?.id }),
          dismiss: dismiss
        )
      )
    } else {
      self.modifier(
        OldAlertModifier(
          viewStore: ViewStore(store, removeDuplicates: { $0?.id == $1?.id }),
          dismiss: dismiss
        )
      )
    }
  }
}

// NB: Workaround for iOS 14 runtime crashes during iOS 15 availability checks.
@available(iOS 15, macOS 12, tvOS 15, watchOS 8, *)
private struct NewAlertModifier<Action>: ViewModifier {
  @StateObject var viewStore: ViewStore<AlertState<Action>?, Action>
  let dismiss: Action

  func body(content: Content) -> some View {
    content.alert(
      (viewStore.state?.title).map { Text($0) } ?? Text(""),
      isPresented: viewStore.binding(send: dismiss).isPresent(),
      presenting: viewStore.state,
      actions: {
        ForEach($0.buttons) {
          Button($0) { viewStore.send($0) }
        }
      },
      message: { $0.message.map { Text($0) } }
    )
  }
}

private struct OldAlertModifier<Action>: ViewModifier {
  @ObservedObject var viewStore: ViewStore<AlertState<Action>?, Action>
  let dismiss: Action

  func body(content: Content) -> some View {
    content.alert(item: viewStore.binding(send: dismiss)) { state in
      Alert(state) { viewStore.send($0) }
    }
  }
}