将类从 @ObservableObject 重构为 @Observable 的正确方法是什么？

Question

我想使用@Observable而不是@ObservableObject重构以下代码。

import Foundation
import FirebaseAuth

enum AuthenticationState {
  case unauthenticated
  case authenticating
  case authenticated
}

enum AuthenticationFlow {
  case login
  case signUp
}

@MainActor
class AuthenticationViewModel: ObservableObject {
  @Published var email = ""
  @Published var password = ""
  @Published var confirmPassword = ""

  @Published var flow: AuthenticationFlow = .login

  @Published var isValid = false
  @Published var authenticationState: AuthenticationState = .unauthenticated
  @Published var errorMessage = ""
  @Published var user: User?
  @Published var displayName = ""


  init() {
    registerAuthStateHandler()

    $flow
      .combineLatest($email, $password, $confirmPassword)
      .map { flow, email, password, confirmPassword in
        flow == .login
        ? !(email.isEmpty || password.isEmpty)
        : !(email.isEmpty || password.isEmpty || confirmPassword.isEmpty)
      }
      .assign(to: &$isValid)
  }

  private var authStateHandler: AuthStateDidChangeListenerHandle?

  func registerAuthStateHandler() {
    if authStateHandler == nil {
      authStateHandler = Auth.auth().addStateDidChangeListener { auth, user in
        self.user = user
        self.authenticationState = user == nil ? .unauthenticated : .authenticated
        self.displayName = user?.displayName ?? user?.email ?? ""
      }
    }
  }

  func switchFlow() {
    flow = flow == .login ? .signUp : .login
    errorMessage = ""
  }

  private func wait() async {
    do {
      print("Wait")
      try await Task.sleep(nanoseconds: 1_000_000_000)
      print("Done")
    }
    catch {
      print(error.localizedDescription)
    }
  }

  func reset() {
    flow = .login
    email = ""
    password = ""
    confirmPassword = ""
  }
}

我在苹果关于“从 Observable 对象协议迁移到 Observable 宏”的文档的帮助下重构如下。

import Foundation
import FirebaseAuth

enum AuthenticationState {
  case unauthenticated
  case authenticating
  case authenticated
}

enum AuthenticationFlow {
  case login
  case signUp
}

@MainActor
@Observable class AuthenticationViewModel {
  var email = ""
  var password = ""
  var confirmPassword = ""

  var flow: AuthenticationFlow = .login

  var isValid = false
  var authenticationState: AuthenticationState = .unauthenticated
  var errorMessage = ""
  var user: User?
  var displayName = ""


  init() {
    registerAuthStateHandler()

    $flow
      .combineLatest($email, $password, $confirmPassword)
      .map { flow, email, password, confirmPassword in
        flow == .login
        ? !(email.isEmpty || password.isEmpty)
        : !(email.isEmpty || password.isEmpty || confirmPassword.isEmpty)
      }
      .assign(to: &$isValid)
  }

  private var authStateHandler: AuthStateDidChangeListenerHandle?

  func registerAuthStateHandler() {
    if authStateHandler == nil {
      authStateHandler = Auth.auth().addStateDidChangeListener { auth, user in
        self.user = user
        self.authenticationState = user == nil ? .unauthenticated : .authenticated
        self.displayName = user?.displayName ?? user?.email ?? ""
      }
    }
  }

  func switchFlow() {
    flow = flow == .login ? .signUp : .login
    errorMessage = ""
  }

  private func wait() async {
    do {
      print("Wait")
      try await Task.sleep(nanoseconds: 1_000_000_000)
      print("Done")
    }
    catch {
      print(error.localizedDescription)
    }
  }

  func reset() {
    flow = .login
    email = ""
    password = ""
    confirmPassword = ""
  }
}

最具挑战性的部分是

$flow
      .combineLatest($email, $password, $confirmPassword)
      .map { flow, email, password, confirmPassword in
        flow == .login
        ? !(email.isEmpty || password.isEmpty)
        : !(email.isEmpty || password.isEmpty || confirmPassword.isEmpty)
      }
      .assign(to: &$isValid)

重构此代码的正确方法是什么？

Xcode 抱怨它无法在范围内找到 $flow。

Answer 1

通常你会从 ObservableObject 重构为 .task 例如

.task(id: loginConfig) {
    user = await loginController.login(loginInfo)
}

其中 loginConfig 是一个包含字段的结构，控制器是一个带有异步函数的环境结构，因此我可以模拟它以进行预览。