Life & Code

<> 例子2 QueryInterface的實現

今天一大早就把例子完成了

#include <objbase.h>
#include <unknwn.h>
#include <iostream>
using namespace std;

interface IX:IUnknown{
 virtual void __stdcall FX() = 0;
};

interface IY:IUnknown{
 virtual void __stdcall FY() = 0;
};

interface IZ:IUnknown{
 virtual void __stdcall FZ() = 0;
};

extern const IID IID_IX;
extern const IID IID_IY;
extern const IID IID_IZ;

class CA:public IX,
   public IY
{
 virtual void __stdcall FY() {cout <<"CA::FY"<<endl; }
 virtual void __stdcall FX() {cout <<"CA::FX"<<endl; }      
        virtual HRESULT STDMETHODCALLTYPE QueryInterface(
            /* [in] */ REFIID riid,
            /* [iid_is][out] */ void __RPC_FAR *__RPC_FAR *ppvObject)
  {
   if(riid == IID_IX)
   {
    *ppvObject = static_cast<IX*>(this);
   }
   else if(riid == IID_IY)
   {
    *ppvObject = static_cast<IY*>(this);
   }
   else if(riid == IID_IUnknown)
   {
    *ppvObject = static_cast<IX*>(this);
   }
   else
   {
    *ppvObject = NULL;
    return E_NOINTERFACE;
   }
   reinterpret_cast<IUnknown *>(*ppvObject)->AddRef();
   return S_OK;

  }
       
  virtual ULONG STDMETHODCALLTYPE AddRef( void){ return 0; }
       
  virtual ULONG STDMETHODCALLTYPE Release( void) {return 0; } 

};

IUnknown * CreateInstance()
{
     IUnknown * pI = static_cast <IX*>(new CA);
     pI->AddRef();
     return pI;
}

// {1A5EE493-AD77-4224-9A78-5F2DD3874714}
static const IID IID_IX =
{ 0x1a5ee493, 0xad77, 0x4224, { 0x9a, 0x78, 0x5f, 0x2d, 0xd3, 0x87, 0x47, 0x14 } };

// {AB55D03D-2160-4197-8AD2-36A36E33F69B}
static const IID IID_IY =
{ 0xab55d03d, 0x2160, 0x4197, { 0x8a, 0xd2, 0x36, 0xa3, 0x6e, 0x33, 0xf6, 0x9b } };

// {5443E124-25A6-451e-A634-2BA392788C38}
static const IID IID_IZ =
{ 0x5443e124, 0x25a6, 0x451e, { 0xa6, 0x34, 0x2b, 0xa3, 0x92, 0x78, 0x8c, 0x38 } };

int _tmain(int argc, _TCHAR* argv[])
{
    HRESULT  hr;
    IUnknown *pUnknown = CreateInstance();
    IX *pIX = NULL;
    hr = pUnknown->QueryInterface(IID_IX,(void **)(&pIX));
    if(SUCCEEDED(hr))
    {
         pIX->FX();
    }

    IY *pIY = NULL;
    hr = pUnknown->QueryInterface(IID_IY,(void **)(&pIY));
    if(SUCCEEDED(hr))
    {
         pIY->FY();
    }
     delete pUnknown;
     return 0;
}

/*
口QueryInterface 返回的總是同一IUnknown指針
口若客戶曾經獲取過某個接口．那么它將總能獲取此接口。
口客戶可以再次獲取已經擁有的接口。
口客戶可以返回到起始接口。
口若能夠從某個接口獲取某特定接口，那么可以從任意接口都將可以獲取此接口
下面我們將詳細討論這些規則。
*/

posted on 2006-03-02 09:35 橙子 閱讀(2093) 評論(1)  編輯 收藏 引用