从函数返回流

问题描述

我正在使用 riverpod 进行状态管理。

class SignInStateNotifier extends StateNotifier<SignInFormStates> {
  SignInStateNotifier(this._authFacade) : super(SignInFormStates.initial());

  final IAuthFacade _authFacade;

  void mapEventToState(SignInFormEvents signInFormEvents) {
    state = signInFormEvents.when(
        emailChanged: (value) => state.copyWith(
              emailAddress: EmailAddress(value),authFailureOrSuccess: none(),),passwordChanged: (value) => state.copyWith(
              password: Password(value),signInWithEmailAndPasswordpressed: () async* {
          yield* _performActionOnAuthFacade(
              _authFacade.signInWithEmailAndPassword);
        });
  }

我在这里遇到错误

signInWithEmailAndPasswordpressed: () async* {
              yield* _performActionOnAuthFacade(
                  _authFacade.signInWithEmailAndPassword);
            });

参数类型 'Stream Function()' 不能是 分配给参数类型“SignInFormStates Function()”。

我的 __performActionOnAuthFacade 函数

Stream<SignInFormStates> _performActionOnAuthFacade(
    Future<Either<AuthFailure,Unit>> Function({
      @required EmailAddress emailAddress,@required Password password,})
        forwardCall,) async* {
    Either<AuthFailure,Unit> failureOrSuccess;
    if (state.emailAddress.isValid() && state.password.isValid()) {
      yield state.copyWith(
        isSubmitting: true,);
      failureOrSuccess = await _authFacade.registerWithEmailAndPassword(
          emailAddress: state.emailAddress,password: state.password);
    }
    yield state.copyWith(
        isSubmitting: false,showErrorMessage: true,authFailureOrSuccess: optionOf(failureOrSuccess));
  }

请给出解决此错误的解决方案。提前致谢。

解决方法

如果您想使用 StateNotifier 执行此操作，而无需使用 Stream 来更改状态，您需要执行以下操作：

class SignInFormStateNotifier extends StateNotifier<SignInFormState> {
  final IAuthFacade _authFacade;

  SignInFormStateNotifier(this._authFacade) : super(SignInFormState.initial());

  Future handleEvent(SignInFormEvent event) async {
    event.map(
      // email changed
      emailChanged: (event) {
        state = state.copyWith(
          emailAddress: EmailAddress(event.email),authFailureOrSuccessOption: none(),);
      },// password changed
      passwordChanged: (event) {
        state = state.copyWith(
          password: Password(event.password),// register with email and password
      registerWithEmailAndPassword: (event) async {
        await _performActionWithEmailAndPassword(
          _authFacade.registerWithEmailAndPassword,// sign in with email and password
      signInWithEmailAndPassword: (event) async {
        await _performActionWithEmailAndPassword(
          _authFacade.signInWithEmailAndPassword,// sign in with Google
      signInWithGoogle: (event) async {
        state = state.copyWith(
          isSubmitting: true,);
        final result = await _authFacade.signInWithGoogle();

        state = state.copyWith(
          isSubmitting: false,authFailureOrSuccessOption: some(result),);
  }

  Future _performActionWithEmailAndPassword(
    Future<Either<AuthFailure,Unit>> Function({
      @required EmailAddress emailAddress,@required Password password,})
        action,) async {
    Either<AuthFailure,Unit> result;
    final isEmailValid = state.emailAddress.isValid();
    final isPasswordValid = state.password.isValid();

    if (isEmailValid && isPasswordValid) {
      state = state.copyWith(
        isSubmitting: true,);

      result = await action(
        emailAddress: state.emailAddress,password: state.password,);

      state = state.copyWith(
        authFailureOrSuccessOption: some(result),);
    }
    state = state.copyWith(
      isSubmitting: false,showErrorMessages: true,authFailureOrSuccessOption: optionOf(result),);
  }
}

,

我不知道您的 SignInFormStates 类，但它不希望在 signInWithEmailAndPasswordPressed 中调用 Stream 函数，但可能是一个空的 voidCallback？

state = signInFormEvents.when(
        emailChanged: (value) => state.copyWith(
              emailAddress: EmailAddress(value),authFailureOrSuccess: none(),),passwordChanged: (value) => state.copyWith(
              password: Password(value),signInWithEmailAndPasswordPressed: () => () async* {  //so a SignInFormStates Function() calls your stream function
          yield* _performActionOnAuthFacade(
              _authFacade.signInWithEmailAndPassword);
        });

但是在那之后它仍然有机会给你一些其他错误，告诉你状态期望是 SignInFormStates 类型并且你传递给它一个流函数，或者它实际上等待流完成并且返回产生的新状态，唯一要做的就是尝试看看会发生什么