c# - 使抽象方法具有覆盖的主体

Question

我有我的Beverage 类，它有一些 getter/setter 来处理饮料的大小。这个程序与装饰器模式有关，所以我想结合一些同名方法的行为。

我的意图是拥有一个方法体，允许我获取饮料的大小，但随后，我希望能够在子类上覆盖该行为。

总而言之，我想要一个方法:

• 如果没有被重写，就如同父类中的方法一样
• 如果被重写，则表现得像被编码一样

我所做的是创建一个名为 getSizeOfBeverage 的方法，它的行为类似于我的“旧”getSize 所做的，并使 getSize 成为“新的” "方法抽象所以我可以覆盖它，但我想要一个不暗示新方法名称的解决方案。

这是我的代码:

using System;

namespace Decorator
{
    class Program
    {
        static void Main(string[] args)
        {
            Beverage beverage = new Espresso("small");
            beverage = new Whip(beverage);
            Console.WriteLine(beverage.getDescription() + " $" + beverage.cost());
        }
    }

    abstract class Beverage
    {
      private string description;
      private string size;

      public Beverage()
      {
        setDescription("Unknown beverage");
      }

      public double getCost()
      {
        return cost();
      }

      public abstract double cost();

      public abstract string getDescription();

      public void setDescription(string desc)
      {
        description = desc;
      }

      public string getSizeOfBeverage()
      {
        return size;
      }

      public abstract string getSize();

      public void setSize(string sz)
      {
        size = sz;
      }
    }

    class Espresso : Beverage
    {
      public Espresso(string sz)
      {
        setSize(sz);
        setDescription("Espresso");
      }

      public override double cost()
      {
        return 1.9;
      }

      public override string getDescription()
      {
        return getDescription();
      }

      public override string getSize()
      {
        return getSizeOfBeverage();
      }
    }

    abstract class CondimentDecorator : Beverage
    {
      public abstract override string getSize();
    }

    class Whip : CondimentDecorator
    {
      private Beverage beverage;

      public Whip(Beverage bv)
      {
        beverage = bv;
      }

      public override double cost()
      {
        if (getSize() == "small")
        {
          return 0.1 + beverage.cost();
        }
        else if (getSize() == "medium")
        {
          return 0.15 + beverage.cost();
        }
        else
        {
          return 0.2 + beverage.cost();
        }
      }

      public override string getDescription()
      {
        return beverage.getDescription() + ", whip";
      }

      public override string getSize()
      {
        return beverage.getSizeOfBeverage();
      }
    }
}

Answer 1

if not overriden, just behaves as the method in the parent class if

overriden, behaves like it is coded

每个 virtual 方法都是这样工作的:

如果它被重写，它将表现得像它被编码的那样，如果不只是表现得像父类中的方法一样

来自 virtual 的文档

The virtual keyword is used to modify a method, property, indexer, orevent declaration and allow for it to be overridden in a derivedclass. For example, this method can be overridden by any class thatinherits it:

和abstract

When an instance method declaration includes an abstract modifier,that method is said to be an abstract method. Although an abstractmethod is implicitly also a virtual method, it cannot have themodifier virtual. An abstract method declaration introduces a newvirtual method but does not provide an implementation of that method.Instead, non-abstract derived classes are required to provide theirown implementation by overriding that method. Because an abstractmethod provides no actual implementation, the method-body of anabstract method simply consists of a semicolon.

查看 virtual and abstract methods in C# 之间的区别