c# - 如何克隆从 C# 中的抽象类派生的类实例的通用列表？

Question

我有一个基类:abstract class Base和一些派生类:class Derived: Base ，所有数据成员都在基类中。我有另一个通用列表:List<Base> list .现在我想执行 Clone() list 上的操作。我读过 this thread但是发现我的情况有点复杂。由于基类是抽象的，因此不能通过复制构造函数或实现 ICloneable 来克隆列表的元素。界面。但是由于所有的数据成员都在基类中，所以在派生类中一次又一次地编写相同的代码来克隆是多余的。完成这项工作的最佳方法是什么？感谢您提供提示。

更新:附上简化的源代码

public class Point : ICloneable
{
    public int X { get; set; }
    public int Y { get; set; }

    public Point(int x, int y)
    { X = x; Y = y; }

    public Point(Point p)
    {
        X = p.X; Y = p.Y;
    }

    public object Clone()
    {
        return MemberwiseClone();
    }
}

public abstract class ObjectThatHasPosition : ICloneable
{
    public Point CurrentPosition { get; set; }
    public ObjectThatHasPosition(Point p)
    { CurrentPosition = new Point(p); }
    public object Clone()
    {
        return MemberwiseClone();
    }
}

public class Man : ObjectThatHasPosition
{
    public Man(Point p) : base(p) { }
}

static class Extensions
{
    public static List<ObjectThatHasPosition> Clone(this List<ObjectThatHasPosition> src)
    {
        List<ObjectThatHasPosition> dst = new List<ObjectThatHasPosition>(src.Count);
        src.ForEach((item) => { dst.Add((ObjectThatHasPosition)item.Clone()); });
        return dst;
    }
}

    static void Main(string[] args)
    {
        List<ObjectThatHasPosition> firstList = new List<ObjectThatHasPosition>();
        firstList.Add(new Man(new Point(0, 0)));
        List<ObjectThatHasPosition> anotherList = firstList.Clone();
        firstList[0].CurrentPosition.X = 1;
    }

可以看到两个列表的元素是相同的。

Answer 1

我不明白为什么 Base 不能实现 ICloneable:

public abstract class Base : ICloneable
{
    public object Clone()
    {
        return MemberwiseClone();
    }
}

当在派生类上调用时，它仍然会返回正确的实例(即与现有对象相同的类型)。派生类中的任何字段也将被复制——尽管是一种浅显的方式。举个具体的例子:

using System;

public abstract class BaseClass : ICloneable
{
    public object Clone()
    {
        return MemberwiseClone();
    }
}

public class Derived : BaseClass
{
    private readonly string name;

    public Derived(string name)
    {
        this.name = name;
    }

    public override string ToString()
    {
        return "Derived with name " + name;
    }
}

class Test
{
    static void Main(string[] args)
    {
        BaseClass b = new Derived("fred");

        object clone = b.Clone();
        Console.WriteLine(clone.ToString());
    }
}

编辑:我怀疑你想要这样的东西:

public abstract class ObjectThatHasPosition : ICloneable
{
    public Point CurrentPosition { get; set; }
    public ObjectThatHasPosition(Point p)
    {
        CurrentPosition = p; 
    }

    public object Clone()
    {
        var clone = (ObjectThatHasPosition) MemberwiseClone();
        clone.CurrentPosition = (Point) CurrentPosition.Clone();
    }
}