Flutter错误处理与结果返回插件 error_or_result 的使用

error_or_result 是一个用于优雅地处理错误（如领域错误）的库，通过将返回的结果作为正常程序流程的一部分来处理，从而减少抛出异常的数量。该库受到了 C# 版本 的启发。

示例代码

下面是一个完整的示例，展示了如何在 Flutter 应用中使用 error_or_result 插件来处理错误和返回结果。

定义实体类

import 'package:error_or_result/error_or_result.dart';

class Employee {
  int id;
  String name;
  int? managerId;

  Employee({
    required this.id,
    required this.name,
    this.managerId,
  });
}

class Company {
  final String name;
  List<Employee> employees;

  Company({required this.name, required this.employees});
}

定义错误类型

class CompanyDomainErrors {
  static ErrorResult notHeadOfCompany = ErrorResult.validation(
      code: "CompanyError.NotHeadOfCompany",
      description: "The employee is not the head of the company.");
  static ErrorResult isNotRegisteredEmployee = ErrorResult.notFound(
      code: "CompanyError.DoesntExist",
      description: "The employee is not registered in the company.");
}

创建服务类

class CompanyDomainService {
  static ErrorOr<Employee> getCompanyEmployeeById(int employeeId) {
    var doesEmployeeExist = carCompany.employees.map((e) => e.id).toList().remove(employeeId);
    if (doesEmployeeExist != null) {
      Employee employee = carCompany.employees.firstWhere((employee) => employee.id == employeeId);
      return ErrorOr.fromResult(employee);
    }
    return ErrorOr.fromErrors([CompanyDomainErrors.isNotRegisteredEmployee]);
  }

  static ErrorOr<bool> isHeadOfCompany(Employee employee) {
    if (employee.managerId == null && carCompany.employees.contains(employee)) {
      return ErrorOr.fromResult(true);
    }
    return ErrorOr.fromError(CompanyDomainErrors.notHeadOfCompany);
  }
}

初始化公司数据

var ali = Employee(id: 1, name: "Ali");
var john = Employee(id: 2, name: "John", managerId: 1);
var alex = Employee(id: 3, name: "Alex", managerId: 2);
var jane = Employee(id: 4, name: "Jane", managerId: 3);
var carCompany = Company(name: "SmartX Cars Dealership", employees: [ali, john, alex, jane]);

使用 ErrorOr<T> 类处理结果

void main() {
  // Example for ErrorOr<T> class approach
  ErrorOr<bool> isHeadOFCompanyResult = CompanyDomainService.isHeadOfCompany(john);
  if (isHeadOFCompanyResult.isError) {
    print(isHeadOFCompanyResult.firstError.description);
  } else {
    print(isHeadOFCompanyResult.result);
  }

  ErrorOr<Employee> employeeResult = CompanyDomainService.getCompanyEmployeeById(2);
  if (employeeResult.isError) {
    print(employeeResult.firstError.code);
  } else {
    print(employeeResult.result.name);
  }
}

使用 ErrorOrValue<T> 类处理结果

class CompanyDomainErrorOrValueErrors {
  static VFailure notHeadOfCompany = VFailure.validation(
      code: "CompanyError.NotHeadOfCompany",
      description: "The employee is not the head of the company.");
  static VFailure isNotRegisteredEmployee = VFailure.notFound(
      code: "CompanyError.DoesntExist",
      description: "The employee is not registered in the company.");
}

class CompanyDomainServiceErrorOrValue {
  static ErrorOrValue<Employee> getCompanyEmployeeById(int employeeId) {
    var doesEmployeeExist = carCompany.employees.map((e) => e.id).toList().remove(employeeId);
    if (doesEmployeeExist != null) {
      Employee employee = carCompany.employees.firstWhere((employee) => employee.id == employeeId);
      return ErrorOrValue.fromResult(employee);
    }
    return ErrorOrValue.fromErrors([CompanyDomainErrorOrValueErrors.isNotRegisteredEmployee]);
  }

  static ErrorOrValue<bool> isHeadOfCompany(Employee employee) {
    if (employee.managerId == null && carCompany.employees.contains(employee)) {
      return ErrorOrValue.fromResult(true);
    }
    return ErrorOrValue.fromErrors([CompanyDomainErrorOrValueErrors.notHeadOfCompany]);
  }
}

void main() {
  // Example for ErrorOrValue<T> class approach
  ErrorOrValue<bool> isBossOfCompanyResult = CompanyDomainServiceErrorOrValue.isHeadOfCompany(john);
  if (isBossOfCompanyResult.isError) {
    print(isBossOfCompanyResult.errors.first.description);
  } else {
    print(isBossOfCompanyResult.result);
  }

  ErrorOrValue<Employee> eResult = CompanyDomainServiceErrorOrValue.getCompanyEmployeeById(2);
  if (eResult.isError) {
    print(eResult.errors.first.code);
  } else {
    print(eResult.result.name);
  }
}