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C# 中的猴子修补

发布于 2024-10-09 10:48:04 字数 119 浏览 1 评论 0原文

是否可以在运行时扩展或修改 C# 类的代码？

我的问题具体围绕 Monkey Patching / Duck Punching 或元对象编程 (MOP)，就像 Groovy、Ruby 等脚本语言中发生的那样。

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与他有关 2024-10-16 10:48:04

对于那些今天仍然在这个问题上绊倒的人来说，确实有一个名为 Harmony 的当今库，它相对-直接在运行时启用此类猴子修补。它的重点是视频游戏模组（特别是使用 Unity 构建的游戏），但并没有太多阻止人们在该用例之外使用它。

从他们的 introduction 复制示例，如果您有这样的现有类：

public class SomeGameClass
{
    public bool isRunning;
    public int counter;

    private int DoSomething()
    {
        if (isRunning)
        {
            counter++;
        }
        return counter * 10;
    }
}

那么 Harmony 可以像这样修补它：

using HarmonyLib;
using Intro_SomeGame;

public class MyPatcher
{
    // make sure DoPatching() is called at start either by
    // the mod loader or by your injector

    public static void DoPatching()
    {
        var harmony = new Harmony("com.example.patch");
        harmony.PatchAll();
    }
}

[HarmonyPatch(typeof(SomeGameClass))]
[HarmonyPatch("DoSomething")]
class Patch01
{
    static AccessTools.FieldRef<SomeGameClass, bool> isRunningRef =
        AccessTools.FieldRefAccess<SomeGameClass, bool>("isRunning");

    static bool Prefix(SomeGameClass __instance, ref int ___counter)
    {
        isRunningRef(__instance) = true;
        if (___counter > 100)
            return false;
        ___counter = 0;
        return true;
    }

    static void Postfix(ref int __result)
    {
        __result *= 2;
    }
}

在这里，我们有一个“前缀”补丁，它会在原始方法运行之前插入，允许我们在方法内设置变量，在方法的类上设置字段，甚至完全跳过原始方法。我们还有一个“后缀”补丁，它会在原始方法运行后插入，并且可以操作返回值等内容。

显然，这并不像您可以在 Ruby 中进行的猴子修补那么好，并且有许多警告可能会妨碍它的实用性，具体取决于您的用例，但在您确实需要改变方法的情况下，Harmony 是一种经过验证的方法。

For those still stumbling on this question in the present day, there is indeed a present-day library called Harmony that relatively-straightforwardly enables such monkey-patching at runtime. Its focus is on video game modding (particularly games built with Unity), but there ain't much stopping folks from using it outside of that use case.

Copying the example from their introduction, if you have an existing class like so:

public class SomeGameClass
{
    public bool isRunning;
    public int counter;

    private int DoSomething()
    {
        if (isRunning)
        {
            counter++;
        }
        return counter * 10;
    }
}

Then Harmony can patch it like so:

using HarmonyLib;
using Intro_SomeGame;

public class MyPatcher
{
    // make sure DoPatching() is called at start either by
    // the mod loader or by your injector

    public static void DoPatching()
    {
        var harmony = new Harmony("com.example.patch");
        harmony.PatchAll();
    }
}

[HarmonyPatch(typeof(SomeGameClass))]
[HarmonyPatch("DoSomething")]
class Patch01
{
    static AccessTools.FieldRef<SomeGameClass, bool> isRunningRef =
        AccessTools.FieldRefAccess<SomeGameClass, bool>("isRunning");

    static bool Prefix(SomeGameClass __instance, ref int ___counter)
    {
        isRunningRef(__instance) = true;
        if (___counter > 100)
            return false;
        ___counter = 0;
        return true;
    }

    static void Postfix(ref int __result)
    {
        __result *= 2;
    }
}

Here, we have a "prefix" patch which gets inserted before the original method runs, allowing us to set variables within the method, set fields on the method's class, or even skip the original method entirely. We also have a "postfix" patch which gets inserted after the original method runs, and can manipulate things like the return value.

Obviously this ain't quite as nice as the sorts of monkey-patching you can do in e.g. Ruby, and there are a lot of caveats that might hinder its usefulness depending on your use case, but in those situations where you really do need to alter methods, Harmony's a pretty proven approach to doing so.

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