向CCmdTarget的派生类添加一个接口的实现

作者:  日期:2005-12-8 1:28:28  来源:Internet      点击:次  评论
    DECLARE_INTERFACE_MAP() //声明接口映射
    BEGIN_INTERFACE_PART(TestInterface, IMyTest) //声明实现接口IMyTest的嵌套类
        STDMETHOD(Test)();
    END_INTERFACE_PART(FontNotify2)

(2)CSampleView类实现中加入以下代码:

    BEGIN_INTERFACE_MAP(CSampleView, CCmdTarget)
        INTERFACE_PART(CSampleView, IID_IMyTest, TestInterface)
    END_INTERFACE_MAP()

    STDMETHODIMP_(ULONG) CSampleView::XTestInterface::AddRef( )
    {
        METHOD_PROLOGUE_EX(CSampleView, TestInterface)
        return (ULONG)pThis->ExternalAddRef();
    }

    STDMETHODIMP_(ULONG) CSampleView::XTestInterface::Release( )
    {
        METHOD_PROLOGUE_EX(CSampleView, TestInterface)
        return (ULONG)pThis->ExternalRelease();
    }

    STDMETHODIMP CSampleView::XTestInterface::QueryInterface( REFIID iid, LPVOID FAR* ppvObj )
    {
        METHOD_PROLOGUE_EX(CSampleView, TestInterface)
        return (HRESULT)pThis->ExternalQueryInterface(&iid, ppvObj) ;
    }

    STDMETHODIMP CSampleView::XTestInterface::Test()
    {
        METHOD_PROLOGUE_EX(CSampleView, TestInterface)
        // do something you like
        return S_OK ;
    }

  揭开宏的神秘面纱,看看它到底是什么东西。以下都是简化的版本。

(1)DECLARE_INTERFACE_MAP

struct AFX_INTERFACEMAP_ENTRY
{
    const void* piid;
    // the interface id (IID) (NULL for aggregate)
    size_t nOffset;
    // offset of the interface vtable from m_unknown
};

struct AFX_INTERFACEMAP
{
    const AFX_INTERFACEMAP* (PASCAL* pfnGetBaseMap)(); // NULL is root class
    const AFX_INTERFACEMAP_ENTRY* pEntry; // map for this class
};

#define DECLARE_INTERFACE_MAP() \
private: \
    static const AFX_INTERFACEMAP_ENTRY _interfaceEntries[]; \
protected: \
    static AFX_DATA const AFX_INTERFACEMAP interfaceMap; \
    static const AFX_INTERFACEMAP* PASCAL _GetBaseInterfaceMap(); \
    virtual const AFX_INTERFACEMAP* GetInterfaceMap() const; \

(2)BEGIN_INTERFACE_PART/END_INTERFACE_PART

#define BEGIN_INTERFACE_PART(localClass, baseClass) \// 定义了一个嵌套类
    class X##localClass : public baseClass \
    { \
    public: \
        STDMETHOD_(ULONG, AddRef)(); \
        STDMETHOD_(ULONG, Release)(); \
        STDMETHOD(QueryInterface)(REFIID iid, LPVOID* ppvObj); \

#define END_INTERFACE_PART(localClass) \
    } m_x##localClass; \
    friend class X##localClass; \

(3)BEGIN_INTERFACE_MAP/INTERFACE_PART/END_INTERFACE_MAP

#define offsetof(s,m) (size_t)&(((s *)0)->m)

#define BEGIN_INTERFACE_MAP(theClass, theBase) \
    const AFX_INTERFACEMAP* PASCAL theClass::_GetBaseInterfaceMap() \
        { return &theBase::interfaceMap; } \
    const AFX_INTERFACEMAP* theClass::GetInterfaceMap() const \
        { return &theClass::interfaceMap; } \
    AFX_COMDAT const AFX_DATADEF AFX_INTERFACEMAP theClass::interfaceMap = \
        { &theClass::_GetBaseInterfaceMap, &theClass::_interfaceEntries[0], }; \
    AFX_COMDAT const AFX_DATADEF AFX_INTERFACEMAP_ENTRY theClass::_interfaceEntries[] = \
    { \

#define INTERFACE_PART(theClass, iid, localClass) \
        { &iid, offsetof(theClass, m_x##localClass) }, \

#define END_INTERFACE_MAP() \
        { NULL, (size_t)-1 } \
    }; \

(4)METHOD_PROLOGUE_EX

#define METHOD_PROLOGUE_EX(theClass, localClass) \
    METHOD_PROLOGUE(theClass, localClass) \

#define METHOD_PROLOGUE(theClass, localClass) \
    theClass* pThis = \
        ((theClass*)((BYTE*)this - offsetof(theClass, m_x##localClass))); \
    AFX_MANAGE_STATE(pThis->m_pModuleState) \
    pThis; // avoid warning from compiler \

  METHOD_PROLOGUE最大的作用就是得到pThis指针。该宏用在嵌套类的成员函数中,pThis是其父类的指针,这里也即是CSampleView的this指针。

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