移动构造函数调用基类Move构造函数 [英] Move Constructor calling base-class Move Constructor

问题描述

我有一个基本类，它基本上将一个类附加到一个任意的窗口句柄（例如，HWND，HFONT），并使用策略类附加/分离和销毁：

I have a base class that basically wraps up attaching a class to a arbitrary windows handle (e.g, HWND, HFONT), and uses a policy class to attach/detach and destroy:

// class SmartHandle
template<typename THANDLE, class TWRAPPER, class TPOLICY>
class SmartHandle : boost::noncopyable
{
private:
    TPOLICY*  m_pPolicy;    // Policy
    bool m_bIsTemporary;    // Is this a temporary window?

    SmartHandle();  // no default ctor
    SmartHandle(const SmartHandle<THANDLE, TWRAPPER, TPOLICY>&);    // no cctor
protected:
    THANDLE   m_hHandle;    // Handle to the underlying window

    TPOLICY& policy() {return(*m_pPolicy);};

    // ctor that attaches but is temporary
    SmartHandle(const THANDLE& _handle, bool _temporary) : m_hHandle(_handle)
                                                         , m_bIsTemporary(_temporary)
    {
        m_pPolicy = new TPOLICY(reinterpret_cast<TWRAPPER&>(*this));
        if(_handle)
            m_pPolicy->attach(_handle);
    };  // eo ctor

    // move ctor
    SmartHandle(SmartHandle<THANDLE, TWRAPPER, TPOLICY>&& _rhs) : m_hHandle(_rhs.m_hHandle)
                                                                      , m_bIsTemporary(_rhs.m_bIsTemporary)
    {
        m_pPolicy = new TPOLICY(reinterpret_cast<TWRAPPER&>(*this));
        m_pPolicy->attach(m_hHandle);
        const_cast<SmartHandle&>(_rhs).m_hHandle = NULL;
    };  // eo mtor

    // dtor
    virtual ~SmartHandle()
    {
        if(m_hHandle)
        {
            m_pPolicy->detach(m_hHandle);
            if(!m_bIsTemporary)
                m_pPolicy->destroy(m_hHandle);
            m_hHandle = NULL;
        };
        delete(m_pPolicy);
        m_pPolicy = NULL;
    }; // eo dtor

注意，我已经将复制构造函数私有

Note that I've declared the copy constructor private (with no implementation) as I do not want the class to be copied, but a move is allowed.

我的窗口 class派生自：

My Window class derives from this:

    class GALLOW_API Window : SmartHandle<HWND, Window, detail::_hWndPolicy>
    {
    friend class Application;
    private:
        static LRESULT CALLBACK wndProc(HWND _hWnd, UINT _message, WPARAM _wParam, LPARAM _lParam);

        // no copy/default ctor
        Window();
        Window(const Window&);
    protected:

    public:
        static const String ClassName;
        Window(const HWND& _hWnd);
        Window(const WindowCreateInfo& _createInfo);
        Window(Window&& _rhs);
        virtual ~Window();
    };  // eo class Window

再次复制default / copy ctors。移动构造函数的实现是：

Once again, copy default/copy ctors. The implementation of the move constructor is:

    Window::Window(Window&& _rhs) : SmartHandle(_rhs)
    {
    };  // eo mtor

但是，在编译期间，我在move构造函数的第一行获得以下错误实施：

However, during compilation I get the following error on the first line of the move constructor implementation:

1>c:\\documents\visual studio 2010\projects\gallow\gallow\window.cpp(81): error C2248: 'gallow::SmartHandle<THANDLE,TWRAPPER,TPOLICY>::SmartHandle' : cannot access private member declared in class 'gallow::SmartHandle<THANDLE,TWRAPPER,TPOLICY>'

所以，它似乎是试图调用复制构造函数比移动构造函数。有没有简单的我在这里缺少？

So, it appears as if it is trying to call the copy constructor (which I've declared private) rather than the move constructor. Is there something simple I am missing here?

提前感谢。

编辑：修改mtor非常数，错误仍然存​​在。
EDIT2：我使用Visual C ++ 2010。

Modified mtor so it was non-const, error remains. I am using Visual C++ 2010.

推荐答案

实际上应该是这样的。 b
$ b

actually it should be like this.

Window::Window(Window&& _rhs) : SmartHandle( std::forward<SmartHandle>( _rhs ) )     {     };  // eo mtor 

http://msdn.microsoft.com/en-us/library/ee390914.aspx

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