一般 std::function 成员

Question

我有一个使用 EnumWindows 的 class。因为这需要回调，所以我将它包装成一个不错的小工具 class 类似于：

Class Tools
{
public:
    template<typename WinFunctor>
    std::vector<HWND> FindWindow(WinFunctor Functor);

private:
    BOOL EnumWindowMsgProc(HWND hWnd);
    static BOOL CALLBACK FreeWndProc(HWND hWnd, LPARAM lParam)
    {
        Tools* pThis = (Tools*)lParam;
        return pThis->EnumWindowMsgProc(hWnd);
    }
    std::vector<HWND> m_Windows;
    /*Need to store WinFunctor Here*/
}

BOOL Tools::EnumWindowMsgProc(HWND hWnd)
{
    if(/*Call WinFunctor Member here*/)
    {
        m_Windows.push_back(hWnd);
    }
    return TRUE;
}
template<typename WinFunctor>
std::vector<HWND> Tools::FindWindow(WinFunctor Functor)
{
    m_Windows.clear();
    EnumWindows(FreeWndProc, (LPARAM)this);
    return m_Windows;
}
/*Windows Callbacks must be free (not a class member), 
so I define a static method (free) and forward to my    
member function(not free)*/

WinFunctor 示例：

bool EnumByWindowName(HWND WinHandle,const std::wstring& WinName)
{
    wchar_t Temp[1024]{L'[=12=]'};
    GetWindowText(WinHandle, Temp, 1024);
    if (std::wstring(Temp).compare(WinName.c_str()) == 0)
        return true;
    return false;
}

所需界面示例

Tools ToolInst;
auto Windows=ToolsInst.FindWindow(EnumByWindowName(std::placeholders::_1,"Notepad-Untitled"));

我需要以某种方式将 Functor 存储为成员，以便稍后在回调中调用它，但我不能只模板化 class 因为这需要我创建一个新的工具实例每次我想搜索不同的 window（并且工具 class 拥有比 EnumWindows 更多的功能）。Functor 必须始终接受一个 hWnd，然后可以使用它想要的任何东西对该数据进行操作，并且可能会传递对其采取行动所需的其他参数（例如 WindowName sting）。是否有存储仿函数的方法，而不必每次都创建 class 的新实例。感谢您的帮助

Answer 1

Piotr S 发布的解决方案

Class Tools
{
public:
    typedef std::function<bool(HWND)> WinFunctor;
    std::vector<HWND> FindWindow(const WinFunctor& Functor);

private:
    BOOL EnumWindowMsgProc(HWND hWnd);
    static BOOL CALLBACK FreeWndProc(HWND hWnd, LPARAM lParam)
    {
        Tools* pThis = (Tools*)lParam;
        return pThis->EnumWindowMsgProc(hWnd);
    }
    std::vector<HWND> m_Windows;
    WinFunctor m_WinFunctor;
}

BOOL Tools::EnumWindowMsgProc(HWND hWnd)
{
    if(m_WinFunctor(hWnd))
        m_Windows.push_back(hWnd);
    return TRUE;
}

std::vector<HWND> Tools::FindWindow(const WinFunctor& Functor)
{
    m_Windows.clear();
    m_WinFunctor=Functor;
    EnumWindows(FreeWndProc, (LPARAM)this);
    return m_Windows;
}

接口：

auto Windows = m_Tools.FindParentWindow(std::bind(&WinEnumFunctors::EnumByWindowName, std::placeholders::_1, L"Some WindowName"));

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