如何使可插拔的静态类

问题描述

我知道如何使可插拔的东西在C＃。定义一个接口， Activator.CreateInstance（小于类＆GT;）等，或者我可以明确创建插入类的一个实例的code路径。方法很多。

I know how to make pluggable things in c#. Define an Interface, Activator.CreateInstance(<class>), etc. Or I can have a code path that explicitly creates an instance of the plugged class. Many ways.

但是，如果我想使可插拔的服务是静态的（我知道我可以重构，以便它不是但这不是问题的点）

But what if the service I want to make pluggable is static (I know I could refactor so that it's not but that's not the point of the question)

具体的例子。我有一个类，它提供的磁盘I / O的抽象（读取文件，列出目录，....）。现在，我想这个抽象，供应的文件，比如说，从一个真正的FS，一个数据库的不同实现。

Concrete example. I have a class that provides disk I/O abstraction (Read File, List Directory,....). Now I want different implementations of this abstraction that serves up files from , say, a real FS, a database.

根据奥利维尔Jacot-Descombes的答复，我将有一个文件系统类（即实）这样的

Based on Olivier Jacot-Descombes reply, I will have a FileSystem class (that is real) like this

public static class FileSystem
{
    static IFSImplemenation s_imple;
    static FileSystem()
    {
        if(<some system setting>)
            // converted to singleton instead of static
            s_imple = new OldFileSystem()
        else
            s_imple = new DbFileSystem();
    }

    public static byte[] ReadFile(string path)
    {
        return s_imple.ReadFile(path);
    }

    ...
}

要重申 - 我有一个庞大的身躯code，我不想改变，因此重要的是要保持调用签名是相同的 - 该解决方案实现了。

To reiterate - I have a large body of code that I dont want to change so it was important to keep the calling signature the same - this solution achieves that

推荐答案

使用您的静态类作为门面的非静态实施

Use your static class as facade for non-static implementations

public static class DB
{
    private static IDbInterface _implementation;

    public static void SetImplementation(IDbInterface implementation)
    {
        _implementation = implementation;
    }

    public static Customer GetCustomerByID(int custId)
    {
        return _implementation.GetCustomerByID(custId);
    }

    ...
}

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