解决方法为用例朋友类在C＃ [英] Workaround for an use-case of friend classes in C#

问题描述

考虑以下code模式：

Consider the following code pattern:

// Each foo keeps a reference to its manager
class Foo
{
    private FooManager m_manager;
}

// Manager keeps a list of all foos
class FooManager
{
    private List<Foo> m_foos;
}

问题：没有办法来创建新的Foo和更新两个m_foos列表中FooManager，和m_manager参考在新的Foo实例，而不公开揭露一些下身（和运行有人desyncing列表与实际FOOS的风险） 。

Problem: there is no way to create a new Foo and update both m_foos list in the FooManager, and m_manager reference in the new Foo instance without exposing some privates publicly (and running the risk of someone desyncing the list with actual Foos).

例如。人们可以实现一个构造函数富（FooManager经理）的富。它可以设置m_manager参考，但它没有办法访问m_foos列表。或者，你可以实现在管理CreateFoo（）方法。它可以访问m_foos列表中，但是却没有办法在富设置m_manager。

E.g. one could implement a constructor Foo(FooManager manager) in Foo. It could set m_manager reference, but it has no way to access the m_foos list. Or you could implement CreateFoo() method in the manager. It can access m_foos list, but it has no way to set m_manager in Foo.

在C ++中，人们显然会宣布FooManager富来恩preSS的设计意图的朋友，但是这是不可能在C＃。我也知道，我可以让富的内部类FooManager来获得，但是这不是一个解决方案，或者（如果美孚可能属于多个经理级？）

In C++, one would obviously declare FooManager a friend of Foo to express the design intent, but this is not possible in C#. I also know that I could make Foo an inner class of FooManager to gain access, but this is not a solution either (what if Foo could belong to more than one manager class?)

顺便说一句。我知道在.NET中的内部的访问，但它要求Foo和FooManager自立门户在一个单独的程序，这是不能接受的。

Btw. I know about "internal" access in .NET, but it requires that Foo and FooManager live on their own in a separate assembly, which is not acceptable.

任何解决方法，如果没有做私人的东西公开？

Any workarounds for that without making private stuff public?

推荐答案

如果我所有的正确理解：

If I understand all correctly:

public abstract class FooBus
{
    protected static FooBus m_bus;
}

public sealed class Foo : FooBus
{
    private FooManager m_manager;

    public Foo(FooManager fm)
    {
        if (fm == null)
        {
            throw new ArgumentNullException("Use FooManager.CreateFoo()");
        }

        if (m_bus != fm)
        {
            throw new ArgumentException("Use FooManager.CreateFoo()");
        }

        m_manager = fm;
    }
}

public class FooManager : FooBus
{
    private List<Foo> m_foos = new List<Foo>();

    public Foo CreateFoo()
    {
        m_bus = this;
        Foo f = new Foo(this);
        m_foos.Add(f);
        m_bus = null;

        return f;
    }
}

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