如何在C ++ / CLI中使用boost :: bind来绑定托管类的成员

I am using boost::signal in a native C++ class, and I now I am writing a .NET wrapper in C++/CLI, so that I can expose the native C++ callbacks as .NET events. When I try to use boost::bind to take the address of a member function of my managed class, I get compiler error 3374, saying I cannot take the address of a member function unless I am creating a delegate instance. Does anyone know how to bind a member function of a managed class using boost::bind?

我在本机C ++类中使用boost :: signal,现在我在C ++ / CLI中编写.NET包装器,这样我就可以将本机C ++回调公开为.NET事件。当我尝试使用boost :: bind获取托管类的成员函数的地址时,我得到编译器错误3374,说我不能获取成员函数的地址,除非我创建委托实例。有谁知道如何使用boost :: bind绑定托管类的成员函数?

For clarification, the following sample code causes Compiler Error 3374:

为了澄清,以下示例代码导致编译器错误3374:

#include <boost/bind.hpp>

public ref class Managed
{
public:
    Managed()
    {
        boost::bind(&Managed::OnSomeEvent, this);
    }

    void OnSomeEvent(void)
    {
    }
};

2 个解决方案

#1

While your answer works, it exposes some of your implementation to the world (Managed::OnSomeEvent). If you don't want people to be able to raise the OnChange event willy-nilly by invoking OnSomeEvent(), you can update your Managed class as follows (based on this advice):

虽然您的答案有效,但它会将您的一些实现暴露给全世界(Managed :: OnSomeEvent)。如果您不希望人们通过调用OnSomeEvent()而无所事事地引发OnChange事件,则可以按如下方式更新Managed类(基于此建议):

public delegate void ChangeHandler(void);
typedef void (__stdcall *ChangeCallback)(void);

public ref class Managed
{
public:
    Managed(Native* Nat);
    ~Managed();

    event ChangeHandler^ OnChange;

private:
    void OnSomeEvent(void);
    Native* native;
    Callback* callback;
    GCHandle gch;
};

Managed::Managed(Native* Nat)
 : native(Nat)
{
    callback = new Callback;

    ChangeHandler^ handler = gcnew ChangeHandler( this, &Managed::OnSomeEvent );
    gch = GCHandle::Alloc( handler );
    System::IntPtr ip = Marshal::GetFunctionPointerForDelegate( handler );
    ChangeCallback cbFunc = static_cast<ChangeCallback>( ip.ToPointer() );

    *callback = native->RegisterCallback(boost::bind<void>( cbFunc ) );
}

Managed::~Managed()
{
    native->UnregisterCallback(*callback);
    delete callback;
    if ( gch.IsAllocated )
    {
        gch.Free();
    }
}

void Managed::OnSomeEvent(void)
{
    OnChange();
}

Note the alternate bind<R>() form that's used.

请注意使用的备用bind ()形式。

#2

After googling some more, I finally found a nice blog post about how to do this. The code in that post was a little more than I needed, but the main nugget was to use a global free function that takes an argument of the managed this pointer wrapped in a gcroot<> template. See the SomeEventProxy(...) in the code below for an example. This function then turns around and calls the managed member I was trying to bind. My solution appears below for future reference.

谷歌搜索了一些后,我终于找到了一篇关于如何做到这一点的好文章。该帖子中的代码比我需要的多一点,但主要的核心是使用一个全局*函数,它接受包含在gcroot <>模板中的托管this指针的参数。有关示例,请参阅下面代码中的SomeEventProxy(...)。然后这个函数转过来并调用我试图绑定的托管成员。我的解决方案如下所示,以供将来参

#include <msclr/marshal.h>

#include <boost/bind.hpp>
#include <boost/signal.hpp>
#include <iostream>

#using <mscorlib.dll>

using namespace System;
using namespace msclr::interop;

typedef boost::signal<void (void)> ChangedSignal;
typedef boost::signal<void (void)>::slot_function_type ChangedSignalCB;
typedef boost::signals::connection  Callback;


class Native
{
public:

    void ChangeIt() 
    {
        changed();
    }

    Callback RegisterCallback(ChangedSignalCB Subscriber)
    {
        return changed.connect(Subscriber);
    }

    void UnregisterCallback(Callback CB)
    {
        changed.disconnect(CB);
    }

private:
    ChangedSignal changed;
};



delegate void ChangeHandler(void);


public ref class Managed
{
public:
    Managed(Native* Nat);
    ~Managed();
    void OnSomeEvent(void);

    event ChangeHandler^ OnChange;

private:
    Native* native;
    Callback* callback;
};


void SomeEventProxy(gcroot<Managed^> This)
{
    This->OnSomeEvent();
}


Managed::Managed(Native* Nat)
 : native(Nat)
{
    native = Nat;
    callback = new Callback;
    *callback = native->RegisterCallback(boost::bind( SomeEventProxy, gcroot<Managed^>(this) ) );
}

Managed::~Managed()
{
    native->UnregisterCallback(*callback);
    delete callback;
}

void Managed::OnSomeEvent(void)
{
    OnChange();
}


void OnChanged(void)
{
    Console::WriteLine("Got it!");
}

int main(array<System::String ^> ^args)
{
    Native* native = new Native;
    Managed^ managed = gcnew Managed(native);

    managed->OnChange += gcnew ChangeHandler(OnChanged);

    native->ChangeIt();

    delete native;
    return 0;
}