多级继承可扩展方法

Question

假设我有三个或更多类：工程师：员工：人员。考虑以下示例（假设我现在使用 StringBuilder 和其他更好的做法）

public abstract class Person
{
   public string Name{get;set;}
   public string SaySomething()
   {
      string introduction = "Hello, my name is " + Name + ". ";
      return OnSaySomething(introduction);
   }
   protected virtual string OnSaySomething(string thoughts)
   { return thoughts; }
}

public abstract class Employee : Person
{
   public string Employer{get;set;}

   protected override string OnSaySomething(string thoughts)
   {
      return thoughts + "I work for " + Employer + ".";
   }
}

public class Engineer : Employee
{
   public string Discipline{get;set;}

   protected override string OnSaySomething(string thoughts)
   {
      return thoughts + "My discipline is " + Discipline + ".";
   }
}

结合上面的例子，输出为：

 Engineer engineer = new Engineer();
 engineer.Name = "Dennis Ritchie";
 engineer.Discipline = "Software Engineering";
 Console.WriteLine(engineer.SaySomething());

会产生

Hello, my name is Dennis Ritchie. My discipline is Software Engineering.

是否可以构建这些类以便每个覆盖 "tacks on" 更多功能，从而输出为：

Hello, my name is Dennis Ritchie. I work for . My discipline is Software Engineering.

有没有标准的方法来实现这种想法？我下意识的解决方案是在 Employee 处密封 OnSaySomething() 并引入一个新方法 OnEmployeeSaySomething()，Engineer 会因为它自己的特定逻辑而覆盖它。

这似乎很快就会变得混乱，因为 SaySomething()、OnSaySomething() 和 OnEmployeeSaySomething() 都暴露在 Engineer 处（如果还有另一个级别则更糟等级制度！）。我想知道是否有更好的解决方案。感谢您的关注！

TL;DR：我想在不破坏基本逻辑的情况下进行扩展。但我不希望我的类真的很乱。

编辑：

有人指出了一个好的（也许是显而易见的）解决方案，这是我提供了一个错误示例的错误。相反，假设我们在这种情况下验证一些数据：

public class Level0
{
    public string Data{get;set;}
    public bool IsValid()
    {
        if (Data == null) return false;
        else return OnIsValid();
    }
    protected virtual bool OnIsValid()
    {return true;}  
}
public class Level1 : Level0
{
    public string Data_Level1{get;set;}
    protected override OnIsValid()
    {
        if (Data_level1 == null) return false;
        else return OnLevel1IsValid();
    }
    protected virtual bool OnLevel1IsValid()
    {return true;}
}
public class Level2 : Level1
{
    public string Data_Level2{get;set;}

    protected override OnLevel1IsValid()
    {
        return Data_level2 != null;
    }
}

Answer 1

利用基础：

protected override string OnSaySomething(string thoughts)
   {

      return base.OnSaySomething() + thoughts + "My discipline is " + Discipline + ".";
   }

Answer 2

我不太明白你用 "I want to extend, not override" 是什么意思，因为你显然使用了 "override" 关键字。无论如何，我可以提出以下解决方案：

public abstract class Person
{
   public string Name{get;set;}
   public virtual string SaySomething()
   {
      return = "Hello, my name is " + Name + ". ";
   }
}

public abstract class Employee : Person
{
   public string Employer{get;set;}

   public override string SaySomething()
   {
      return base.SaySomething() + "I work for " + Employer + ". ";
   }
}

public class Engineer : Employee
{
   public string Discipline{get;set;}

   public override string SaySomething()
   {
      return base.SaySomething() + "My discipline is " + Discipline + ". ";
   }
}

Answer 3

您需要调用该函数的基础版本，以便下一个更高级别可以构建它的字符串，然后 return 将其转换为派生版本，以便它可以添加额外的文本。

public abstract class Employee : Person
{
   public string Employer{get;set;}

   protected override string OnSaySomething(string thoughts)
   {
      return base.OnSaySomething(thoughts)+ "I work for " + Employer + ".";
   }
}

public class Engineer : Employee
{
   public string Discipline{get;set;}

   protected override string OnSaySomething(string thoughts)
   {
      return base.OnSaySomething(thoughts) + "My discipline is " + Discipline + ".";
   }
}

编辑：使用您更新后的代码，它仍然是一回事

public class Level1 : Level0
{
    public string Data_Level1{get;set;}
    protected override bool OnIsValid()
    {
        return base.OnIsValid() && Data_level1 != null;
    }
}
public class Level2 : Level1
{
    public string Data_Level2{get;set;}

    protected override OnLevel1IsValid()
    {
        return base.OnIsValid() && Data_level2 != null;
    }
}

EDIT2：要做到这一点 "Automatic" 你几乎已经完成了实施，你可以做的另一件事是标记属性 sealed 所以在链的更下方它不能再次被覆盖，但是我不推荐这种方法，而是使用我之前示例中的覆盖。

public class Level1 : Level0
{
    public string Data_Level1 { get; set; }

    protected override sealed bool OnIsValid()
    {
        if (Data_Level1 == null) return false;
        else return OnLevel1IsValid();
    }

    protected virtual bool OnLevel1IsValid()
    {
        return true;
    }
}

public class Level2 : Level1
{
    public string Data_Level2 { get; set; }

    protected override sealed bool OnLevel1IsValid()
    {
        return Data_Level2 != null;
    }
}

Answer 4

需要调用基础版

protected override string OnSaySomething(string thoughts)
{
      return base.OnSaySomething(thoughts) + "My discipline is " + Discipline + ".";
}

多级继承可扩展方法

Multi-level Inheritance Extensible Methods

.net

c#

hierarchy