Question

我有两个类，Win32和Engine。我正在尝试将我的WindowProc函数从我的Engine类传递给Win32类。我知道typedef WNDPROC被声明为：

typedef LRESULT(CALLBACK *WNDPROC)(HWND, UINT, WPARAM, LPARAM);

我的Win32标头声明为：

// Win32.h
#include <Windows.h>

class Win32
{
    public:
        Win32() {};
        ~Win32() {};

        void Initialize(WNDPROC);

    private:
        // Route messages to non static WindowProc that is declared in Engine class.
        static LRESULT CALLBACK MessageRouter(HWND, UINT, WPARAM, LPARAM);
};

我的Engine类声明为：

// Engine.h
#include "Win32.h"

class Engine
{
    public:
        Engine() {};
        ~Engine() {};

        void Initialize();

    private:
        LRESULT CALLBACK WindowProc(HWND, UINT, WPARAM, LPARAM);

        Win32* m_win32;
};


// Engine.cpp
#include "Engine.h"

void Engine::Initialize()
{
    m_win32 = new Win32;
    m_win32->Initialize(&WindowProc);  // How can I pass this function without making
                                       // it static or global.
}

我的Win32类已经有一个静态MessageRouter，它被赋予WNDCLASSEX。所以我的问题是，如何将Engine :: WindowProc函数传递给Win32类而不将其声明为静态或全局？

Answer 1

您可以使用std::function和std::bind()（在C ++ 11中）或boost::function boost::bind()（在C ++ 03中）。这两者在功能上几乎相同，因此我将展示std::bind()的使用。

以下是根据WNDPROC_FXN定义名为std::function的类型别名的方法：

typedef std::function<LRESULT CALLBACK (HWND, UINT, WPARAM, LPARAM)> WNDPROC_FXN;

您可以在Win32课程中使用它：

class Win32
{
public:
    Win32() {};
    ~Win32() {};

    void Initialize(WNDPROC_FXN);
//                  ^^^^^^^^^^^

private:
    // Route messages to non static WindowProc that is declared in Engine class.
    static LRESULT CALLBACK MessageRouter(HWND, UINT, WPARAM, LPARAM);
};

这就是将成员函数绑定到this指针并将其传递给Win32::Initialize()的方法：

#include <functional>

// ...

void Engine::Initialize()
{
    using namespace std::placeholders;

    m_win32 = new Win32;
    m_win32->Initialize(std::bind(&Engine::WindowProc, this, _1, _2, _3 _4);
//                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
}

Answer 2

为了完整起见，还有一种方法可以用语言结构来完成。此实现使用指向成员函数的指针：

// Win32.h
#include <Windows.h>

class Engine;

class Win32
{
    public:
        Win32() {};
        ~Win32() {};

        void Initialize(LRESULT(CALLBACK Engine::* function)(HWND, UINT, WPARAM, LPARAM));

    private:
        // Route messages to non static WindowProc that is declared in Engine class.
        static LRESULT CALLBACK MessageRouter(HWND, UINT, WPARAM, LPARAM);
};

class Engine
{
    public:
        Engine() {};
        ~Engine() {};

        void Initialize();

    private:
        LRESULT CALLBACK WindowProc(HWND, UINT, WPARAM, LPARAM);

        Win32* m_win32;
};

void Engine::Initialize()
{
    m_win32 = new Win32;
    m_win32->Initialize(&Engine::WindowProc);  // How can I pass this function without making
                                               // it static or global.
}

int main(void)
{
    Engine engine;

    engine.Initialize();

    return 0;
}

将非静态函数指针传递给另一个类？

2 个答案: