COM初学者看看，有助于理解

 

//采用多重继承方式，模拟实现COM接口和COM对象的例子#define IID_IUnknown 1#define IID_IVideo 2#define IID_IAudio 3struct IUnknown {virtual BOOL QueryInterface(int nIid, void  **ppvObj)=0;virtual DWORD Release()=0;virtual DWORD AddRef()=0;};class IVideo:virtual public IUnknown //接口类定义{public:virtual BOOL OpenVideoChannel()=0;virtual BOOL CloseVideoChannel()=0;virtual DWORD GetVideoChannelState()=0;};class IAudio:virtual public IUnknown //接口类定义{virtual BOOL OpenAudioChannel()=0;virtual BOOL CloseAudioChannel()=0;virtual void TransferAudio()=0;virtual DWORD GetAudioChannelState()=0;};class CVisiblePhone:public IAudio,public IVideo //COM对象类定义{public:CVisiblePhone();~CVisiblePhone();public://IUnknown memeber functionHRESULT QueryInterface(int nIid, void  **ppvObj);DWORD Release();DWORD AddRef();//IVudio memeber functionBOOL OpenVideoChannel();BOOL CloseVideoChannel();DWORD GetVideoChannelState();//IAideo memeber functionBOOL OpenAudioChannel();BOOL CloseAudioChannel();void TransferAudio();DWORD GetAudioChannelState();private:DWORD m_Ref;};//实现接口查询函数QueryInterface()HRESULT CVisiblePhone::QueryInterface(int iid,void **ppvObj){if (iid==IID_IUnknown){*ppvObj=(IUnknown *)((IVideo *)this);((IUnknown *)*ppvObj)->AddRef();}else if (iid==IID_IVideo){*ppvObj=(IVideo *)this;((IVideo *)*ppvObj)->AddRef();}else if (iid==IID_IAudio){*ppvObj=(IAudio *)this;((IAudio *)*ppvObj)->AddRef();}else{*ppvObj=NULL;return E_NOINTERFACE;}return S_OK;}

 

 

 

//采用内嵌类的方式在一个COM对象中实现多个接口#define IID_IUnknown 1#define IID_IVideo 2#define IID_IAudio 3class CVisiblePhone//COM对象类定义{public:CVisiblePhone();~CVisiblePhone();public://IUnknown memeber functionHRESULT QueryInterface(int nIid, void  **ppvObj);DWORD Release();DWORD AddRef();//embeded IAudioclass CAudioObj:public IAudio{//IUnknown memeber functionHRESULT QueryInterface(int nIid, void  **ppvObj);DWORD Release();DWORD AddRef();//IAideo memeber functionBOOL OpenAudioChannel();BOOL CloseAudioChannel();void TransferAudio();DWORD GetAudioChannelState();}m_AudioObj;//embeded IVudioclass CVideoObj:public IVideo{//IUnknown memeber functionHRESULT QueryInterface(int nIid, void  **ppvObj);DWORD Release();DWORD AddRef();//IVudio memeber functionBOOL OpenVideoChannel();BOOL CloseVideoChannel();DWORD GetVideoChannelState();}m_VideoObj;private:DWORD m_Ref;};//实现接口查询函数QueryInterface()HRESULT CVisiblePhone::QueryInterface(int iid,void **ppvObj){if (iid==IID_IUnknown){*ppvObj=(IUnknown *)&m_VideoObj;AddRef();}else if (iid==IID_IVideo){*ppvObj=&m_VideoObj;AddRef();}else if (iid==IID_IAudio){*ppvObj=&m_AudioObj;AddRef();}else{*ppvObj=NULL;return E_NOINTERFACE;}return S_OK;}