调用抽象 class 类型 C# 的子实现

Question

我想在具有抽象 class 类型的对象上调用子 class 实现。但是，这并不像我想象的那样有效。有没有办法做到这一点，不需要我在第二个切换语句中切换类型？还是 C# 不允许这种行为？

调用代码：

AbstractParentType wfp;

//Switch on diagram type and select processor
switch (qi.DIAGRAMTYPE)
{
    case 1:
        wfp = new T1(notifications);
        break;
    case 2:
        wfp = new T2(notifications);
        break;
    case 3:
        wfp = new T3(notifications);
        break;
    default:
        throw new Exception("Diagramtype not implemented");
}

bool result = false;
//Switch on action type
switch (qi.Type)
{
    case (int)WorkflowActionType.BelItem:
        //Do some case specific stuff here
        ...
        //Call method
        result = wfp.Meth1();
        break;
    ... (a bunch of cases) ...
    case (int)WorkflowActionType.WordDocument:
        //Do some case specific stuff here
        ...
        //Call method
        result = wfp.Meth10();
        break;
}

然后我们有 classes 实现：

abstract class AbstractClassType {
     public bool Meth1() { ... }
     ...
     public bool Meth10() { ... }
     ...
     public abstract MethX();
     public abstract MethY();
}

class T1 : AbstractClassType  {
     public new Meth1() { ... }
     ...
     public new Meth10() { ... } 
     ...
     public override MethX() { ... }
     public override MethY() { ... }
}

实际的方法确实有参数，我确实想要一些方法（但不是全部）的基本实现。目标是允许继承 classes 到 'extend' 方法行为。

Answer 1

尝试使用 virtual keyword

使用虚拟时，您可以为基础 class 中的方法提供 'default' 实现。像这样：

abstract class AbstractClassType {
    public virtual void MethX(){
        //default implementation here.            
    }
    public virtual void MethY(){
        //another default implementation here!
    }
}

class T1 : AbstractClassType {
    public override void MethX(){
        //base.MethX() would call the logic in the base class. 
    }
    public override void MethY(){ 
        //base.MethY() would call the logic in the base class. 
    }
}

virtual 和 abstract 之间的区别基本上是，abstract 方法不能有基本实现，并且必须被覆盖。

一个virtual方法可以有一个基础实现，不需要重写。

您不需要致电 base.MethX/Y()。如果愿意，您甚至可以赋予该方法全新的含义。

Answer 2

首先，你不能创建一个抽象的对象class，因为它不是真正完整的实体。您将始终需要实例化扩展抽象 class.

的 class 的对象

以下代码显示了使用抽象 classes 时的各种选项，而不是全部选项。

    public abstract class AbstractClass
    {
        public void OnlyInAbstract() {
            Console.WriteLine("You are stuck with OnlyInAbstract in abstract class unless you use new keyword.");
        }

        public virtual void OnlyInAbstractForNow()
        {
            Console.WriteLine("You have reached abstract class for now. However, override me for changed behaviour.");
        }

        public abstract void MustImplement();
    }

    public class FirstChild : AbstractClass
    {
        public override void MustImplement()
        {
            Console.WriteLine("You called MustImplement in FirstChild. Nothing else to see here.");
        }

        public override void OnlyInAbstractForNow()
        {
            base.OnlyInAbstractForNow();
            Console.WriteLine("I see you changed my behaviour in FirstChild to extend it after abstract class was done with.");
        }

        public new void OnlyInAbstract()
        {
            Console.WriteLine("Looks like we are making an all new OnlyInAbstract method in child class.");
        }
    }

    static void Main(string[] args)
    {
        AbstractClass abstractClass = new FirstChild();

        abstractClass.MustImplement();

        abstractClass.OnlyInAbstract();

        (abstractClass as FirstChild).OnlyInAbstract();

        abstractClass.OnlyInAbstractForNow();

        Console.Read();
    }

调用抽象 class 类型 C# 的子实现

Call child implementation of abstract class type C#

c#

inheritance

abstract