如何打破GetOrCreate系列方法的递归循环？

问题背景 #

创建Division时，若未找到对应Director会调用GetOrCreateEmployee创建员工；创建Employee必须关联Position；创建Position又必须依赖Division，三个GetOrCreate方法互相调用形成递归死循环，尝试过标记和方法重载未解决。

原始代码 #

static public Employee GetOrCreateEmployee()
{
    Console.WriteLine("Enter the full name of the teacher:");
    string employeeName = Console.ReadLine();
    Employee employee = DB.employees.FirstOrDefault(e => $"{e.Name} {e.Surname} {e.Patronymic}".ToLower() == employeeName.ToLower());
    if (employee == null)
    {
        Console.WriteLine("Enter the employee's name:");
        string name = Console.ReadLine();

        Console.WriteLine("Enter the employee's last name:");
        string surname = Console.ReadLine();

        Console.WriteLine("Enter the employee's middle name:");
        string patronymic = Console.ReadLine();

        Position position = GetOrCreatePosition();
        employee = new Employee(name, surname, patronymic, position);
        DB.employees.Add(employee);
    }
    return employee;
}

static public Position GetOrCreatePosition()
{
    Console.WriteLine("Enter the title of the position:");
    string jobTitleName = Console.ReadLine();

    Position position = DB.positions.FirstOrDefault(j => j.Title.ToLower() == jobTitleName.ToLower());
    if (position == null)
    {
        position = DB.positions.FirstOrDefault(j => j.Title.ToLower() == jobTitleName.ToLower());
    }

    Console.WriteLine("Enter the title of the position:");
    string name = Console.ReadLine();

    Console.WriteLine("Enter the salary of the position:");
    int.TryParse(Console.ReadLine(), out int salary);

    Console.WriteLine("Enter the name of the department:");
    string subdivisionName = Console.ReadLine();
    Division division = DB.divisions.FirstOrDefault(s => s.Name.ToLower() == subdivisionName.ToLower());
    if (division == null)
    {
        Console.WriteLine("The division was not found. Create it");
        GetOrCreateDivision();
    }
    division = DB.divisions.FirstOrDefault(s => s.Name.ToLower() == subdivisionName.ToLower());
    Position speciality = new Position(name, salary, division);
    DB.positions.Add(speciality);
    Console.WriteLine("The position has been successfully created.");

    return position;
}

static public void GetOrCreateDivision()
{
    Console.WriteLine("Enter the name of the department:");
    string name = Console.ReadLine();

    Console.WriteLine("Enter the last name, first name and patronymic of the director:");
    string directorFullName = Console.ReadLine();
    Employee director = DB.employees.FirstOrDefault(e => $"{e.Name} {e.Surname} {e.Patronymic}" == directorFullName);
    if (director == null)
    {
        Console.WriteLine("The director has not been found. Create it.");
        GetOrCreateEmployee();
        director = DB.employees.Last();
    }

    Console.WriteLine("Enter the name of the organization:");
    string organizationName = Console.ReadLine();
    Organisation organization = DB.organisations.FirstOrDefault(o => o.Name.ToLower() == organizationName.ToLower());
    if (organization == null)
    {
        Console.WriteLine("The organization was not found. Create it");
        GetOrCreateOrganization();
    }
    organization = DB.organisations.FirstOrDefault(o => o.Name.ToLower() == organizationName.ToLower());
    Division subdivision = new Division(name, director, organization);
    DB.divisions.Add(subdivision);
    Console.WriteLine("The division has been successfully created.");
}

解决方案 #

循环的核心是实体间的强制依赖导致创建顺序死锁，以下三种方案可解决问题：

方案1：拆分实体初始化流程，允许临时无依赖实体 #

修改实体类，添加仅包含基础字段的构造函数，先创建核心实体，后续补全关联关系：

1. 给实体添加精简构造函数：

   // Employee允许先创建无职位的实例
   public Employee(string name, string surname, string patronymic)
   {
       Name = name;
       Surname = surname;
       Patronymic = patronymic;
   }
   
   // Position允许先创建无部门的实例
   public Position(string title, int salary)
   {
       Title = title;
       Salary = salary;
   }
   
   // Division允许先创建无负责人的实例
   public Division(string name, Organisation organization)
   {
       Name = name;
       Organisation = organization;
   }
   

2. 调整GetOrCreate方法逻辑：
   • 创建Director时，先存入无Position的Employee
   • 创建Division时，关联已创建的Director
   • 创建Position时，关联已创建的Division
   • 最后统一给Director补全Position信息

方案2：给方法添加重载，跳过强制依赖 #

通过重载方法，允许在特定场景下跳过循环依赖的创建步骤：

1. 修改GetOrCreateEmployee添加重载：

   static public Employee GetOrCreateEmployee(bool requirePosition = true)
   {
       Console.WriteLine("Enter the full name of the teacher:");
       string employeeName = Console.ReadLine();
       Employee employee = DB.employees.FirstOrDefault(e => $"{e.Name} {e.Surname} {e.Patronymic}".ToLower() == employeeName.ToLower());
       if (employee == null)
       {
           Console.WriteLine("Enter the employee's name:");
           string name = Console.ReadLine();
           Console.WriteLine("Enter the employee's last name:");
           string surname = Console.ReadLine();
           Console.WriteLine("Enter the employee's middle name:");
           string patronymic = Console.ReadLine();
   
           if (requirePosition)
           {
               Position position = GetOrCreatePosition();
               employee = new Employee(name, surname, patronymic, position);
           }
           else
           {
               // 创建无职位的Director，后续补充
               employee = new Employee(name, surname, patronymic);
           }
           DB.employees.Add(employee);
       }
       return employee;
   }
   

2. 修改GetOrCreateDivision调用重载：

   static public void GetOrCreateDivision()
   {
       // ... 原有输入部门名称、组织的逻辑 ...
   
       if (director == null)
       {
           Console.WriteLine("The director has not been found. Create it.");
           // 创建无职位的Director，避免触发循环
           director = GetOrCreateEmployee(requirePosition: false);
       }
   
       // ... 创建Division的逻辑 ...
   
       // 后续补全Director的职位
       Console.WriteLine("Do you want to set a position for the director? (Y/N)");
       if (Console.ReadLine().Trim().ToLower() == "y")
       {
           Position directorPosition = GetOrCreatePosition();
           director.Position = directorPosition;
           // 根据你的DB实现更新Employee记录
       }
   }
   

方案3：重构业务依赖，从根源打破循环 #

重新梳理业务逻辑，解除不必要的强制依赖：

• 允许员工入职时暂不分配职位，后续再设置
• 允许部门先创建，后续再指定负责人
  从业务规则层面移除循环依赖的强制要求，彻底避免死循环。

代码冗余修正 #

注意GetOrCreatePosition中有重复无效的查询代码，需删除：

// 这段代码完全冗余，删除
if (position == null)
{
    position = DB.positions.FirstOrDefault(j => j.Title.ToLower() == jobTitleName.ToLower());
}

内容的提问来源于stack exchange，提问作者Versst