類廠是什麼？就是一個工廠用於建立各種產品，將建立好的產品提供給外部使用者使用。其實現如下：

factory.h

#pragma once #include "unknwn.h" class CClassFactory : public IClassFactory { public: CClassFactory(void); virtual ~CClassFactory(void); public: // IUnknown STDMETHOD_(ULONG, AddRef)(); STDMETHOD_(ULONG, Release)(); STDMETHOD(QueryInterface)(REFIID riid, void** ppv); // IClassFactory STDMETHOD(CreateInstance)(IUnknown* pUnkOuter, REFIID riid, void** ppv); STDMETHOD(LockServer)(BOOL fLock); protected: ULONG m_cRef; };

factory.cpp

#include "StdAfx.h" #include "factory.h" CClassFactory::CClassFactory(void) { m_cRef = 0; InterlockedIncrement(&g_cLock); } CClassFactory::~CClassFactory(void) { InterlockedDecrement(&g_cLock); } STDMETHODIMP_(ULONG) CClassFactory::AddRef() { return ++m_cRef; } STDMETHODIMP_(ULONG) CClassFactory::Release() { if(!--m_cRef) delete this; return m_cRef; } STDMETHODIMP CClassFactory::QueryInterface(REFIID riid, void** ppv) { HRESULT hrRet = S_OK; if(IsBadWritePtr(ppv, sizeof(void*))) return E_POINTER; *ppv = NULL; if(IsEqualGUID(riid, IID_IUnknown)) { *ppv = (IUnknown*)this; }else if(IsEqualGUID(riid, IID_IClassFactory)) { *ppv = (IClassFactory*)this; }else { hrRet = E_NOINTERFACE; } if(S_OK == hrRet) ((IUnknown*) *ppv)->AddRef(); return hrRet; } STDMETHODIMP CClassFactory::CreateInstance(IUnknown* pUnkOuter, REFIID riid, void** ppv) { return E_NOINTERFACE; } STDMETHODIMP CClassFactory::LockServer(BOOL fLock) { fLock ? InterlockedIncrement(&g_cLock) : InterlockedDecrement(&g_cLock); return S_OK; }

將類廠加入mycom中

#include "factory.h" STDAPI DllGetClassObject(REFCLSID rclsid ,REFIID riid,void **ppv) { HRESULT hrRet; CClassFactory* pFactory = 0; if(!IsEqualGUID(rclsid, CLSID_MyCOM)) return CLASS_E_CLASSNOTAVAILABLE; if(IsBadWritePtr(ppv, sizeof(void*))) return E_POINTER; pFactory = new CClassFactory; if(NULL == pFactory) return E_OUTOFMEMORY; hrRet = pFactory->QueryInterface(riid, ppv); if(!SUCCEEDED(hrRet)) delete pFactory; return hrRet; }

目前我們實現的這些函式目的是讓系統以為這是一個COM，我們的目的達到了，不過客戶呼叫CoCreateInstance仍然會失敗，那是因為CClassFactory::CreateInstance中我們直接返回了E_NOINTERFACE。