c++ 从静态函数调用非静态函数 [英] c++ calling a non static function from a static function

问题描述

当我尝试调用非静态函数时遇到访问冲突错误.

我的 .h 文件看起来像这样.

类世界{民众:世界();虚拟〜世界()；静态无效回调调度回调(SIMCONNECT_RECV *pData,DWORD cbData,无效 *pContext);无效进程(SIMCONNECT_RECV *pData，DWORD cbData)；虚空 frameEvent();虚空初始化()；};

现在在我的 .cpp 文件中的 init() 函数中，我调用了一个将数据返回给我的回调函数的函数.

SimConnect_CallDispatch(hSimConnect, DispatchCallback, NULL);

将数据发送到 DisPatchCallback 函数.

在这个函数中存在以下代码:

void CALLBACK World::DispatchCallback(SIMCONNECT_RECV *pData,DWORD cbData,无效 *pContext){World *pThis = reinterpret_cast(pContext);pThis->Process(pData, cbData);}

这个函数是一个静态函数，它创建一个 World 对象来调用 Process 函数.

这有效，但它在想要访问 frameEvent 函数的行中断.

void World::Process(SIMCONNECT_RECV *pData, DWORD cbData){HRESULT 小时；开关(pData-> dwID){案例 SIMCONNECT_RECV_ID_EVENT_FRAME:框架事件()；//它在这里中断 frameEvent 是一个非静态函数休息;}}

<块引用>

访问违规读取位置 0x00000000.

有人能指出我解决这个问题的正确方向吗?

如果您想知道我正在为 Microsoft Flight Simulator X 编写插件.

我正在尝试以 oo 的方式实现 simconnect.h.Msdn 显示了我正在尝试实施的示例.

class CName{无效调度()；静态无效调度回调(SIMCONNECT_RECV *pData,DWORD cbData,无效 *pContext);无效进程(SIMCONNECT_RECV *pData，DWORD cbData)；处理 hSimConnect；//使用 SimConnect_Open 设置此值.};void CName::Dispatch(){::SimConnect_Dispatch(hSimConnect, &CName;::DispatchCallback, this);}//静态函数void CName::DispatchCallback(SIMCONNECT_RECV *pData,DWORD cbData,无效 *pContext){CName *pThis = reinterpret_cast(pContext);pThis->Process(pData, cbData);}void CName::Process(SIMCONNECT_RECV *pData, DWORD cbData){//处理 SimConnect 数据}

我希望我提供了足够的信息.

解决方案

您将 NULL 作为上下文参数传递给 SimConnect_CallDispatch，因此您的回调不知道哪个调用 Process 的 World 对象——如果你不告诉它怎么可能?更改调用以将 this 作为上下文参数传入，就像示例一样:

SimConnect_CallDispatch(hSimConnect, DispatchCallback, this);

I'm experiencing an access violation error when I try to call non static function.

my .h file looks like this.

class World
{
public:
    World();
    virtual ~World();
    static void CALLBACK DispatchCallback(
        SIMCONNECT_RECV *pData,
        DWORD cbData,
        void *pContext
    );
    void Process(SIMCONNECT_RECV *pData, DWORD cbData);
    virtual void frameEvent();
    virtual void init();
};

Now in my .cpp file the init() function I call a function that return data to my callback function.

SimConnect_CallDispatch(hSimConnect, DispatchCallback, NULL);

Which sends data to the DisPatchCallback function.

In this function the following code resides:

void CALLBACK World::DispatchCallback(
    SIMCONNECT_RECV *pData,
    DWORD cbData,
    void *pContext)
{
    World *pThis = reinterpret_cast<World*>(pContext);
    pThis->Process(pData, cbData);
}

this function is a static function which creates a World object to call the Process function.

This works but it break on the line where it wants to access the frameEvent function.

void World::Process(SIMCONNECT_RECV *pData, DWORD cbData)
{
    HRESULT hr;

    switch(pData->dwID)
    {
    case SIMCONNECT_RECV_ID_EVENT_FRAME:
        frameEvent(); //it breaks here frameEvent is a non static function
        break;
    }
}

Access violation reading location 0x00000000.

Can someone point me to the right direction as to solve this issue.?

If you wonder I'm writing a plugin for Microsoft Flight Simulator X.

I'm trying to implement simconnect.h in a oo way. Msdn shows an example that I'm trying to implement.

class CName
{
    void Dispatch();
    static void DispatchCallback(
        SIMCONNECT_RECV *pData,
        DWORD cbData,
        void *pContext
    );
    void Process(SIMCONNECT_RECV *pData, DWORD cbData);

    HANDLE hSimConnect; // use SimConnect_Open to set this value.
};

void CName::Dispatch()
{
    ::SimConnect_Dispatch(hSimConnect, &CName;::DispatchCallback, this);
}

// static function
void CName::DispatchCallback(
    SIMCONNECT_RECV *pData,
    DWORD cbData,
    void *pContext)
{
    CName *pThis = reinterpret_cast<CName*>(pContext);
    pThis->Process(pData, cbData);
}

void CName::Process(SIMCONNECT_RECV *pData, DWORD cbData)
{
    // do processing of SimConnect data
}

I hope I gave enough information.

解决方案

You're passing NULL as the context parameter to SimConnect_CallDispatch, so your callback has no idea which World object to call Process on -- how could it possibly if you don't tell it? Change the call to pass in this as the context parameter, like the example does:

SimConnect_CallDispatch(hSimConnect, DispatchCallback, this);

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