SwiftUI .alert(item:) for multiple types of Error

ErrorAlerts.swift

//
//  ContentView.swift
//  ErrorAlert
//
//  Created by Ethan Huang on 2022/6/4.
//

import SwiftUI

enum AError: Error {
  case a1, a2, a3

  var message: String {
    switch self {
    case .a1:
      return "A1"
    case .a2:
      return "A2"
    case .a3:
      return "A3"
    }
  }
}

enum BError: Error {
  case b1, b2, b3

  var message: String {
    switch self {
    case .b1:
      return "B1"
    case .b2:
      return "B2"
    case .b3:
      return "B3"
    }
  }
}

struct CError: Error {
  var message: String { "C" }
}

struct ContentView: View {
  enum AlertItem: Identifiable {
    case a(AError)
    case b(BError)
    case c(CError)

    var id: String {
      switch self {
      case .a: return "a"
      case .b: return "b"
      case .c: return "c"
      }
    }
  }

  @State private var alertItem: AlertItem?

  var body: some View {
    VStack(spacing: 8) {
      Button("A1", action: { alertItem = .a(.a1)})
      Button("A2", action: { alertItem = .a(.a2)})
      Button("A3", action: { alertItem = .a(.a3)})
      Button("B1", action: { alertItem = .b(.b1)})
      Button("B2", action: { alertItem = .b(.b2)})
      Button("B3", action: { alertItem = .b(.b3)})
      Button("C", action: { alertItem = .c(.init())})
    }
    .font(.title)
    .alert(item: $alertItem) { item in
      switch item {
      case let .a(a):
        return Alert(title: Text("A"), message: Text(a.message))
      case let .b(b):
        return Alert(title: Text("B"), message: Text(b.message))
      case let .c(c):
        return Alert(title: Text("C"), message: Text(c.message))
      }
    }
  }
}

struct ContentView_Previews: PreviewProvider {
  static var previews: some View {
    ContentView()
  }
}