在以基本情况为参数的函数中传递派生类

Question

I am writing a C# program that is a basic text rpg game. When I save the game, I want to pass the character into a save function that will then get the data from the character and write it into an xml file. I have one base class Character and three derived classes: Knight , Rogue , and Wizard . They each have a special int that I want to write to an xml file.

private void Save(Character c, string file) {
    //Sample part of writing the data
    XmlNode nodeName = playerData.CreateElement("name");
    nodeName.AppendChild(playerData.CreateTextNode(c.name));
    nodeDetails.AppendChild(nodeName);
}

I want to pass in a Knight , Rogue , or Wizard into this function and be able to get any variables in the derived classes that are not in the base class. Is there a way to do this?

Answer 1

Yes, through the use of casting.

private void Save(Character c, string file)
{
    if(c is Knight)
    {
        k = (Knight)c;
        // Do whatever with k
    }
    else if (c is Rogue)
    {
        r = (Rogue)c;
        // Do whatever with k
    }
}

However, this undermines the polymorphic structure you have set up - the whole point of polymorphism is that you shouldn't have to do this.

It would be better practice if the Character class had an abstract or virtual method that returned the data needed to save. Each subclass would override this method to return the required information (including anything special for that subclass), so you would never need to check what type of Character was passed in.

Answer 2

See if this helps

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            Rogue rogue = new Rogue();
            Save(rogue, "1234");
        }
        static void Save(Character c, string file)
        {
            if(c.GetType() == typeof(Knight))
            {
            }
            if (c.GetType() == typeof(Rogue))
            {
            }
            if (c.GetType() == typeof(Wizard))
            {
            }


        }
    }

    public class Character
    {
    }
    public class Knight : Character
    {
    }
    public class Rogue : Character
    {
    }
    public class Wizard : Character
    {
    }
}