通过ATL实现类厂和组件的创建

类工厂的实现，组件的创建过程
1. 在*_Server.cpp 中有

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1. BEGIN_OBJECT_MAP(ObjectMap)  
2.     OBJECT_ENTRY(CLSID_Math, CMath)  
3. END_OBJECT_MAP()  

BEGIN_OBJECT_MAP(ObjectMap) OBJECT_ENTRY(CLSID_Math, CMath)END_OBJECT_MAP() 

展开后是这样：

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1. struct _ATL_OBJMAP_ENTRY30  
2. {  
3.     const CLSID* pclsid;  
4.     HRESULT (WINAPI *pfnUpdateRegistry)(BOOL bRegister);  
5.     _ATL_CREATORFUNC* pfnGetClassObject;  
6.     _ATL_CREATORFUNC* pfnCreateInstance;  
7.     IUnknown* pCF;  
8.     DWORD dwRegister;  
9.     _ATL_DESCRIPTIONFUNC* pfnGetObjectDescription;  
10.     _ATL_CATMAPFUNC* pfnGetCategoryMap;  
11.     void (WINAPI *pfnObjectMain)(bool bStarting);  
12. };  
13. static ATL::_ATL_OBJMAP_ENTRY ObjectMap[] =  
14. {  
15.     {  
16.         &CLSID_Math,  
17.         CMath::UpdateRegistry,  
18.         CMath::_ClassFactoryCreatorClass::CreateInstance,  
19.         CMath::_CreatorClass::CreateInstance,  
20.         NULL,  
21.         0,  
22.         CMath::GetObjectDescription,  
23.         CMath::GetCategoryMap,  
24.         CMath::ObjectMain  
25.     },  
26.     {NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL}  
27. };  

struct _ATL_OBJMAP_ENTRY30{ const CLSID* pclsid; HRESULT (WINAPI *pfnUpdateRegistry)(BOOL bRegister); _ATL_CREATORFUNC* pfnGetClassObject; _ATL_CREATORFUNC* pfnCreateInstance; IUnknown* pCF; DWORD dwRegister; _ATL_DESCRIPTIONFUNC* pfnGetObjectDescription; _ATL_CATMAPFUNC* pfnGetCategoryMap; void (WINAPI *pfnObjectMain)(bool bStarting);};static ATL::_ATL_OBJMAP_ENTRY ObjectMap[] ={ { &CLSID_Math, CMath::UpdateRegistry, CMath::_ClassFactoryCreatorClass::CreateInstance, CMath::_CreatorClass::CreateInstance, NULL, 0, CMath::GetObjectDescription, CMath::GetCategoryMap, CMath::ObjectMain }, {NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL}}; 

定义了一个_ATL_OBJMAP_ENTRY 类型的全局数组变量 ObjectMap
然后在 Dll 被载入时用这个数组初始化全局的 _Module 变量

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1. CComModule _Module;  
2. BOOL WINAPI DllMain(HINSTANCE hInstance, DWORD dwReason, LPVOID /*lpReserved*/)  
3. {//......  
4.     if (dwReason == DLL_PROCESS_ATTACH)  
5.     {  
6.         _Module.Init(ObjectMap, hInstance);  
7.     }  
8. }  
9. inline HRESULT CComModule::Init(_ATL_OBJMAP_ENTRY* p, HINSTANCE /*h*/, const GUID* plibid) throw()  
10. {//......  
11.     m_pObjMap = p;  
12.     _ATL_OBJMAP_ENTRY* pEntry = m_pObjMap;  
13.     while (pEntry->pclsid != NULL)  
14.     {  
15.         pEntry->pfnObjectMain(true); //这里就是 CMath::ObjectMain  
16.         pEntry++;  
17.     }  
18. }  

CComModule _Module;BOOL WINAPI DllMain(HINSTANCE hInstance, DWORD dwReason, LPVOID /*lpReserved*/){//...... if (dwReason == DLL_PROCESS_ATTACH) { _Module.Init(ObjectMap, hInstance); }}inline HRESULT CComModule::Init(_ATL_OBJMAP_ENTRY* p, HINSTANCE /*h*/, const GUID* plibid) throw(){//...... m_pObjMap = p; _ATL_OBJMAP_ENTRY* pEntry = m_pObjMap; while (pEntry->pclsid != NULL) { pEntry->pfnObjectMain(true); //这里就是 CMath::ObjectMain pEntry++; }} 


当用户代码中调用 CoCreateInstance 时
HRESULT hr = CoCreateInstance( CLSID_Math,
                                  NULL,
                                  CLSCTX_INPROC,
                                  IID_IMath,
                                  (void**) &pMath );

Dll 中的 DllGetClassObject 会被调用，最终调用 CMath::_ClassFactoryCreatorClass::CreateInstance 创建CMath组件

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1. STDAPI DllGetClassObject(REFCLSID rclsid, REFIID riid, LPVOID* ppv)  
2. {  
3.     return _Module.GetClassObject(rclsid, riid, ppv);  
4. }  
5. inline HRESULT CComModule::GetClassObject(REFCLSID rclsid, REFIID riid, LPVOID* ppv) throw()  
6. {  
7.     _ATL_OBJMAP_ENTRY* pEntry = m_pObjMap;  
8.     while (pEntry->pclsid != NULL)  
9.     {  
10.         if ((pEntry->pfnGetClassObject != NULL) && InlineIsEqualGUID(rclsid, *pEntry->pclsid))  
11.         {  
12.             //pEntry->pfnGetClassObject == CMath::_ClassFactoryCreatorClass::CreateInstance  
13.             //pEntry->pfnCreateInstance == CMath::_CreatorClass::CreateInstance  
14.             pEntry->pfnGetClassObject(pEntry->pfnCreateInstance, __uuidof(IUnknown), (LPVOID*)&pEntry->pCF);  
15.             pEntry->pCF->QueryInterface(riid, ppv);  
16.             break;  
17.         }  
18.         pEntry++;  
19.     }  
20. }  

STDAPI DllGetClassObject(REFCLSID rclsid, REFIID riid, LPVOID* ppv){ return _Module.GetClassObject(rclsid, riid, ppv);}inline HRESULT CComModule::GetClassObject(REFCLSID rclsid, REFIID riid, LPVOID* ppv) throw(){ _ATL_OBJMAP_ENTRY* pEntry = m_pObjMap; while (pEntry->pclsid != NULL) { if ((pEntry->pfnGetClassObject != NULL) && InlineIsEqualGUID(rclsid, *pEntry->pclsid)) { //pEntry->pfnGetClassObject == CMath::_ClassFactoryCreatorClass::CreateInstance //pEntry->pfnCreateInstance == CMath::_CreatorClass::CreateInstance pEntry->pfnGetClassObject(pEntry->pfnCreateInstance, __uuidof(IUnknown), (LPVOID*)&pEntry->pCF); pEntry->pCF->QueryInterface(riid, ppv); break; } pEntry++; }} 


接下来看 CComCoClass 又是如何帮助实现 CMath::_ClassFactoryCreatorClass::CreateInstance 创建类厂的

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1. class ATL_NO_VTABLE CMath :  
2.    public CComObjectRootEx<CComSingleThreadModel>,  
3.    public CComCoClass<CMath, &CLSID_Math>,  
4.    //......  
5. {  
6. }  
7. template <class T, const CLSID* pclsid = &CLSID_NULL> //T = CMath, pclsid = CLSID_Math  
8. class CComCoClass  
9. {  
10. public:  
11.     //DECLARE_CLASSFACTORY()  
12.     //DECLARE_AGGREGATABLE(T)  
13.     typedef ATL::CComCreator< ATL::CComObjectCached< ATL::CComClassFactory > > _ClassFactoryCreatorClass;  
14.     typedef ATL::CComCreator2< ATL::CComCreator< ATL::CComObject< x > >, ATL::CComCreator< ATL::CComAggObject< x > > > _CreatorClass;  
15.     typedef T _CoClass;  
16.     template <class Q>  
17.     static HRESULT CreateInstance(IUnknown* punkOuter, Q** pp)  
18.     {  
19.         return T::_CreatorClass::CreateInstance(punkOuter, __uuidof(Q), (void**) pp);  
20.     }  
21. };  

class ATL_NO_VTABLE CMath : public CComObjectRootEx<CComSingleThreadModel>, public CComCoClass<CMath, &CLSID_Math>, //......{}template <class T, const CLSID* pclsid = &CLSID_NULL> //T = CMath, pclsid = CLSID_Mathclass CComCoClass{public: //DECLARE_CLASSFACTORY() //DECLARE_AGGREGATABLE(T) typedef ATL::CComCreator< ATL::CComObjectCached< ATL::CComClassFactory > > _ClassFactoryCreatorClass; typedef ATL::CComCreator2< ATL::CComCreator< ATL::CComObject< x > >, ATL::CComCreator< ATL::CComAggObject< x > > > _CreatorClass; typedef T _CoClass; template <class Q> static HRESULT CreateInstance(IUnknown* punkOuter, Q** pp) { return T::_CreatorClass::CreateInstance(punkOuter, __uuidof(Q), (void**) pp); }}; 

可见在 CComCoClass 中有两个typedef的定义，
_ClassFactoryCreatorClass 用于创建类厂
而 _CreatorClass用于创建组件实例
DllGetClassObject 最终调用了其中的 _ClassFactoryCreatorClass 的 CreateInstance函数创建类厂

将 _ClassFactoryCreatorClass 展开

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1. //typedef ATL::CComCreator< ATL::CComObjectCached< ATL::CComClassFactory > > _ClassFactoryCreatorClass;  
2. template <class T1> //T1 = ATL::CComObjectCached< ATL::CComClassFactory > 类厂  
3.                     //T1 = ATL::CComCreator< ATL::CComObject< CMath > >, ATL::CComCreator< ATL::CComAggObject< CMath > > 组件  
4. class CComCreator  
5. {  
6. public:  
7.     static HRESULT WINAPI CreateInstance(void* pv, REFIID riid, LPVOID* ppv)  
8.     {  
9.         *ppv = NULL;  
10.         HRESULT hRes = E_OUTOFMEMORY;  
11.         T1* p =  new T1(pv)); //这里创建了组件或类厂  
12.         if (p != NULL)  
13.         {  
14.             p->SetVoid(pv); //pv = CMath::_CreatorClass::CreateInstance  
15.             p->InternalFinalConstructAddRef();  
16.             hRes = p->_AtlInitialConstruct();  
17.             if (SUCCEEDED(hRes))  
18.                 hRes = p->FinalConstruct();  
19.             if (SUCCEEDED(hRes))  
20.                 hRes = p->_AtlFinalConstruct();  
21.             p->InternalFinalConstructRelease();  
22.             if (hRes == S_OK)  
23.                 hRes = p->QueryInterface(riid, ppv); //获取组件接口指针  
24.             if (hRes != S_OK)  
25.                 delete p;  
26.         }  
27.         return hRes;  
28.     }  
29. };  

//typedef ATL::CComCreator< ATL::CComObjectCached< ATL::CComClassFactory > > _ClassFactoryCreatorClass;template <class T1> //T1 = ATL::CComObjectCached< ATL::CComClassFactory > 类厂 //T1 = ATL::CComCreator< ATL::CComObject< CMath > >, ATL::CComCreator< ATL::CComAggObject< CMath > > 组件class CComCreator{public: static HRESULT WINAPI CreateInstance(void* pv, REFIID riid, LPVOID* ppv) { *ppv = NULL; HRESULT hRes = E_OUTOFMEMORY; T1* p = new T1(pv)); //这里创建了组件或类厂 if (p != NULL) { p->SetVoid(pv); //pv = CMath::_CreatorClass::CreateInstance p->InternalFinalConstructAddRef(); hRes = p->_AtlInitialConstruct(); if (SUCCEEDED(hRes)) hRes = p->FinalConstruct(); if (SUCCEEDED(hRes)) hRes = p->_AtlFinalConstruct(); p->InternalFinalConstructRelease(); if (hRes == S_OK) hRes = p->QueryInterface(riid, ppv); //获取组件接口指针 if (hRes != S_OK) delete p; } return hRes; }}; 

DllGetClassObject 调用

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1. //pEntry->pfnGetClassObject(pEntry->pfnCreateInstance, __uuidof(IUnknown), (LPVOID*)&pEntry->pCF);  
2. CMath::_ClassFactoryCreatorClass::CreateInstance (CMath::_CreatorClass::CreateInstance, __uuidof(IUnknown), (LPVOID*)NULL);  

//pEntry->pfnGetClassObject(pEntry->pfnCreateInstance, __uuidof(IUnknown), (LPVOID*)&pEntry->pCF);CMath::_ClassFactoryCreatorClass::CreateInstance (CMath::_CreatorClass::CreateInstance, __uuidof(IUnknown), (LPVOID*)NULL); 

然后在这里面创建了类厂 ：ATL::CComObjectCached< ATL::CComClassFactory >* p = new ATL::CComObjectCached< ATL::CComClassFactory >(pv));
最终获得类厂的接口 ：p->QueryInterface(riid, ppv);

类厂类是ATL::CComClassFactory 它的定义

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1. typedef HRESULT (WINAPI _ATL_CREATORFUNC)(void* pv, REFIID riid, LPVOID* ppv);  
2. class CComClassFactory :  
3.     public IClassFactory,  
4.     public CComObjectRootEx<CComGlobalsThreadModel>  
5. {  
6. public:  
7.     BEGIN_COM_MAP(CComClassFactory)  
8.         COM_INTERFACE_ENTRY(IClassFactory)  
9.     END_COM_MAP()  
10.      
11.     STDMETHOD(CreateInstance)(LPUNKNOWN pUnkOuter, REFIID riid, void** ppvObj)  
12.     {  
13.         HRESULT hRes = E_POINTER;  
14.         *ppvObj = NULL;  
15.         if ((pUnkOuter != NULL) && !InlineIsEqualUnknown(riid)) //检查参数  
16.         {  
17.             ATLTRACE(atlTraceCOM, 0, _T("CComClassFactory: asked for non IUnknown interface while creating an aggregated object"));  
18.             hRes = CLASS_E_NOAGGREGATION;  
19.         }  
20.         else  
21.             hRes = m_pfnCreateInstance(pUnkOuter, riid, ppvObj);  
22.         return hRes;  
23.     }  
24.     void SetVoid(void* pv) //pv = CMath::_CreatorClass::CreateInstance  
25.     {  
26.         m_pfnCreateInstance = (_ATL_CREATORFUNC*)pv;  
27.     }  
28.     _ATL_CREATORFUNC* m_pfnCreateInstance;  
29. };  

typedef HRESULT (WINAPI _ATL_CREATORFUNC)(void* pv, REFIID riid, LPVOID* ppv);class CComClassFactory : public IClassFactory, public CComObjectRootEx<CComGlobalsThreadModel>{public: BEGIN_COM_MAP(CComClassFactory) COM_INTERFACE_ENTRY(IClassFactory) END_COM_MAP() STDMETHOD(CreateInstance)(LPUNKNOWN pUnkOuter, REFIID riid, void** ppvObj) { HRESULT hRes = E_POINTER; *ppvObj = NULL; if ((pUnkOuter != NULL) && !InlineIsEqualUnknown(riid)) //检查参数 { ATLTRACE(atlTraceCOM, 0, _T("CComClassFactory: asked for non IUnknown interface while creating an aggregated object")); hRes = CLASS_E_NOAGGREGATION; } else hRes = m_pfnCreateInstance(pUnkOuter, riid, ppvObj); return hRes; } void SetVoid(void* pv) //pv = CMath::_CreatorClass::CreateInstance { m_pfnCreateInstance = (_ATL_CREATORFUNC*)pv; } _ATL_CREATORFUNC* m_pfnCreateInstance;}; 


这里面有趣的是 SetVoid(void* pv) 它将 CMath::_CreatorClass::CreateInstance 传给了类厂指针成员变量 _ATL_CREATORFUNC* m_pfnCreateInstance

然后，在调用类厂 CreateInstance 创建对象实例时， 它会在检查参数后，调用 CMath::_CreatorClass::CreateInstance
那再看看 CMath::_CreatorClass::CreateInstance 会是如何实现创建组件实例

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1. typedef ATL::CComCreator2< ATL::CComCreator< ATL::CComObject< x > >, ATL::CComCreator< ATL::CComAggObject< x > > > _CreatorClass;  
2. template <class T1, class T2> //T1 = ATL::CComCreator< ATL::CComObject< CMath > >, T2 = ATL::CComCreator< ATL::CComAggObject< CMath > >  
3. class CComCreator2  
4. {  
5. public:  
6.     static HRESULT WINAPI CreateInstance(void* pv, REFIID riid, LPVOID* ppv)  
7.     {  
8.         ATLASSERT(ppv != NULL);  
9.         return (pv == NULL) ?  
10.             ATL::CComCreator< ATL::CComObject< CMath > >::CreateInstance(NULL, riid, ppv) :  
11.             ATL::CComCreator< ATL::CComAggObject< CMath > >::CreateInstance(pv, riid, ppv);  
12.     }  
13. };  

typedef ATL::CComCreator2< ATL::CComCreator< ATL::CComObject< x > >, ATL::CComCreator< ATL::CComAggObject< x > > > _CreatorClass;template <class T1, class T2> //T1 = ATL::CComCreator< ATL::CComObject< CMath > >, T2 = ATL::CComCreator< ATL::CComAggObject< CMath > >class CComCreator2{public: static HRESULT WINAPI CreateInstance(void* pv, REFIID riid, LPVOID* ppv) { ATLASSERT(ppv != NULL); return (pv == NULL) ? ATL::CComCreator< ATL::CComObject< CMath > >::CreateInstance(NULL, riid, ppv) : ATL::CComCreator< ATL::CComAggObject< CMath > >::CreateInstance(pv, riid, ppv); }}; 

它会通过pv参数判断组件是否组合，然后选择相应的创建模板类

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总结一下类厂和组件的创建过程

类厂创建过程：
1. 在*_Server.cpp 中定义CComModule _Module 全局变量和一个数组，里面填入组件创建的相关函数信息

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1. CComModule _Module;  
2. BEGIN_OBJECT_MAP(ObjectMap)  
3.     OBJECT_ENTRY(CLSID_Math, CMath)  
4. END_OBJECT_MAP()  

CComModule _Module;BEGIN_OBJECT_MAP(ObjectMap) OBJECT_ENTRY(CLSID_Math, CMath)END_OBJECT_MAP() 

2. Dll 加载时完成_Module的初始化

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1. BOOL WINAPI DllMain(HINSTANCE hInstance, DWORD dwReason, LPVOID )  
2. {  
3.     if (dwReason == DLL_PROCESS_ATTACH)  
4.     {  
5.         _Module.Init(ObjectMap, hInstance);  
6.     }  
7. }  
8. inline HRESULT CComModule::Init(_ATL_OBJMAP_ENTRY* p, HINSTANCE , const GUID* plibid) throw()  
9. {  
10.     m_pObjMap = p;  
11.     //......  
12. }  

BOOL WINAPI DllMain(HINSTANCE hInstance, DWORD dwReason, LPVOID ){ if (dwReason == DLL_PROCESS_ATTACH) { _Module.Init(ObjectMap, hInstance); }}inline HRESULT CComModule::Init(_ATL_OBJMAP_ENTRY* p, HINSTANCE , const GUID* plibid) throw(){ m_pObjMap = p; //......} 

3. 用户调用 CoCreateInstance 时，dll导出函数 DllGetClassObject 会被调用

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1. STDAPI DllGetClassObject(REFCLSID rclsid, REFIID riid, LPVOID* ppv)  
2. {  
3.     return _Module.GetClassObject(rclsid, riid, ppv);  
4. }  
5. //rclsid = CLSID_Math  
6. inline HRESULT CComModule::GetClassObject(REFCLSID rclsid, REFIID riid, LPVOID* ppv) throw()  
7. {//......  
8.     _ATL_OBJMAP_ENTRY* pEntry = m_pObjMap;  
9.     while (pEntry->pclsid != NULL)  
10.     {  
11.         if ((pEntry->pfnGetClassObject != NULL) && InlineIsEqualGUID(rclsid, *pEntry->pclsid))  
12.         {  
13.             //pEntry->pfnGetClassObject == CMath::_ClassFactoryCreatorClass::CreateInstance  
14.             //pEntry->pfnCreateInstance == CMath::_CreatorClass::CreateInstance  
15.             hr = pEntry->pfnGetClassObject(pEntry->pfnCreateInstance, __uuidof(IUnknown), (LPVOID*)&pEntry->pCF);  
16.             break;  
17.         }  
18.         pEntry++;  
19.     }  
20. }  

STDAPI DllGetClassObject(REFCLSID rclsid, REFIID riid, LPVOID* ppv){ return _Module.GetClassObject(rclsid, riid, ppv);}//rclsid = CLSID_Mathinline HRESULT CComModule::GetClassObject(REFCLSID rclsid, REFIID riid, LPVOID* ppv) throw(){//...... _ATL_OBJMAP_ENTRY* pEntry = m_pObjMap; while (pEntry->pclsid != NULL) { if ((pEntry->pfnGetClassObject != NULL) && InlineIsEqualGUID(rclsid, *pEntry->pclsid)) { //pEntry->pfnGetClassObject == CMath::_ClassFactoryCreatorClass::CreateInstance //pEntry->pfnCreateInstance == CMath::_CreatorClass::CreateInstance hr = pEntry->pfnGetClassObject(pEntry->pfnCreateInstance, __uuidof(IUnknown), (LPVOID*)&pEntry->pCF); break; } pEntry++; }} 

4. DllGetClassObject 会导致 CMath::_ClassFactoryCreatorClass::CreateInstance 的调用

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1. CMath::_ClassFactoryCreatorClass 类型是 CComCreator， 也就是 CComCreator::CreateInstance 被调用，创建了类厂  
2. //typedef ATL::CComCreator< ATL::CComObjectCached< ATL::CComClassFactory > > _ClassFactoryCreatorClass;  
3. template <class T1> //T1 = ATL::CComObjectCached< ATL::CComClassFactory > 类厂  
4. class CComCreator  
5. {//......  
6.     static HRESULT WINAPI CreateInstance(void* pv, REFIID riid, LPVOID* ppv)  
7.     {  
8.         *ppv = NULL;  
9.         HRESULT hRes = E_OUTOFMEMORY;  
10.         T1* p =  new T1(pv)); //这里创建了类厂  
11.         if (p != NULL)  
12.         {  
13.             p->SetVoid(pv); //pv = CMath::_CreatorClass::CreateInstance  
14.             p->QueryInterface(riid, ppv); //获取组件接口指针  
15.             //......  
16.         }  
17.     }  
18. };  

CMath::_ClassFactoryCreatorClass 类型是 CComCreator， 也就是 CComCreator::CreateInstance 被调用，创建了类厂//typedef ATL::CComCreator< ATL::CComObjectCached< ATL::CComClassFactory > > _ClassFactoryCreatorClass;template <class T1> //T1 = ATL::CComObjectCached< ATL::CComClassFactory > 类厂class CComCreator{//...... static HRESULT WINAPI CreateInstance(void* pv, REFIID riid, LPVOID* ppv) { *ppv = NULL; HRESULT hRes = E_OUTOFMEMORY; T1* p = new T1(pv)); //这里创建了类厂 if (p != NULL) { p->SetVoid(pv); //pv = CMath::_CreatorClass::CreateInstance p->QueryInterface(riid, ppv); //获取组件接口指针 //...... } }};

*********************************************************************************

组件的创建过程：
1. CComCreator::CreateInstance 创建类厂后，会调用 SetVoid(pv) 将组件创建的函数指针创给了类工厂

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1. class CComClassFactory : //.....  
2. {//.....  
3.     void SetVoid(void* pv) //pv = CMath::_CreatorClass::CreateInstance  
4.     {  
5.         m_pfnCreateInstance = (_ATL_CREATORFUNC*)pv;  
6.     }  
7.     _ATL_CREATORFUNC* m_pfnCreateInstance;  
8. };  

class CComClassFactory : //.....{//..... void SetVoid(void* pv) //pv = CMath::_CreatorClass::CreateInstance { m_pfnCreateInstance = (_ATL_CREATORFUNC*)pv; } _ATL_CREATORFUNC* m_pfnCreateInstance;}; 

2. 用户调用的 CoCreateInstance， 在成功创建类厂后，会调用类厂的 CreateInstance接口

[cpp] view plaincopyprint?

1. class CComClassFactory : //.....  
2. {//.....  
3.     STDMETHOD(CreateInstance)(LPUNKNOWN pUnkOuter, REFIID riid, void** ppvObj)  
4.     {  
5.         HRESULT hRes = E_POINTER;  
6.         *ppvObj = NULL;  
7.         if ((pUnkOuter != NULL) && !InlineIsEqualUnknown(riid)) //检查参数  
8.         {  
9.             ATLTRACE(atlTraceCOM, 0, _T("CComClassFactory: asked for non IUnknown interface while creating an aggregated object"));  
10.             hRes = CLASS_E_NOAGGREGATION;  
11.         }  
12.         else  
13.             hRes = m_pfnCreateInstance(pUnkOuter, riid, ppvObj); //调用组件创建函数  
14.         return hRes;  
15.     }  
16.     _ATL_CREATORFUNC* m_pfnCreateInstance; //m_pfnCreateInstance = CMath::_CreatorClass::CreateInstance  
17. };  

class CComClassFactory : //.....{//..... STDMETHOD(CreateInstance)(LPUNKNOWN pUnkOuter, REFIID riid, void** ppvObj) { HRESULT hRes = E_POINTER; *ppvObj = NULL; if ((pUnkOuter != NULL) && !InlineIsEqualUnknown(riid)) //检查参数 { ATLTRACE(atlTraceCOM, 0, _T("CComClassFactory: asked for non IUnknown interface while creating an aggregated object")); hRes = CLASS_E_NOAGGREGATION; } else hRes = m_pfnCreateInstance(pUnkOuter, riid, ppvObj); //调用组件创建函数 return hRes; } _ATL_CREATORFUNC* m_pfnCreateInstance; //m_pfnCreateInstance = CMath::_CreatorClass::CreateInstance}; 

3. 类厂的 CreateInstance 会调用通过 SetVoid 获取的组件创建的函数指针， 也就是CMath::_CreatorClass::CreateInstance

[cpp] view plaincopyprint?

1. //typedef ATL::CComCreator2< ATL::CComCreator< ATL::CComObject< CMath > >, ATL::CComCreator< ATL::CComAggObject< CMath > > > _CreatorClass;  
2. template <class T1, class T2> //T1 = ATL::CComCreator< ATL::CComObject< CMath > >, T2 = ATL::CComCreator< ATL::CComAggObject< CMath > >  
3. class CComCreator2  
4. {  
5. public:  
6.     static HRESULT WINAPI CreateInstance(void* pv, REFIID riid, LPVOID* ppv)  
7.     {  
8.         ATLASSERT(ppv != NULL);  
9.         return (pv == NULL) ?  
10.             ATL::CComCreator< ATL::CComObject< CMath > >::CreateInstance(NULL, riid, ppv) :  
11.             ATL::CComCreator< ATL::CComAggObject< CMath > >::CreateInstance(pv, riid, ppv);  
12.     }  
13. };  

//typedef ATL::CComCreator2< ATL::CComCreator< ATL::CComObject< CMath > >, ATL::CComCreator< ATL::CComAggObject< CMath > > > _CreatorClass;template <class T1, class T2> //T1 = ATL::CComCreator< ATL::CComObject< CMath > >, T2 = ATL::CComCreator< ATL::CComAggObject< CMath > >class CComCreator2{public: static HRESULT WINAPI CreateInstance(void* pv, REFIID riid, LPVOID* ppv) { ATLASSERT(ppv != NULL); return (pv == NULL) ? ATL::CComCreator< ATL::CComObject< CMath > >::CreateInstance(NULL, riid, ppv) : ATL::CComCreator< ATL::CComAggObject< CMath > >::CreateInstance(pv, riid, ppv); }}; 

4. CComCreator2 会通过检查pv参数，确定是创建组合对象还是非组合对象，最终还是通过 CComCreator 创建组件

[cpp] view plaincopyprint?

1. //ATL::CComCreator< ATL::CComObject< CMath > >::CreateInstance(NULL, riid, ppv);  
2. template <class T1> //T1 = ATL::CComCreator< ATL::CComObject< CMath > > 或 ATL::CComCreator< ATL::CComAggObject< CMath > > 创建组件                     
3. class CComCreator  
4. {//.....  
5.     static HRESULT WINAPI CreateInstance(void* pv, REFIID riid, LPVOID* ppv)  
6.     {  
7.         *ppv = NULL;  
8.         HRESULT hRes = E_OUTOFMEMORY;  
9.         //ATL::CComObject< CMath > *p = new ATL::CComObject< CMath > (pv);  
10.         T1* p =  new T1(pv)); //这里创建了组件或类厂  
11.         //.....  
12.         hRes = p->QueryInterface(riid, ppv); //获取组件接口指针  
13.         return hRes;  
14.     }  
15. };  

//ATL::CComCreator< ATL::CComObject< CMath > >::CreateInstance(NULL, riid, ppv);template <class T1> //T1 = ATL::CComCreator< ATL::CComObject< CMath > > 或 ATL::CComCreator< ATL::CComAggObject< CMath > > 创建组件 class CComCreator{//..... static HRESULT WINAPI CreateInstance(void* pv, REFIID riid, LPVOID* ppv) { *ppv = NULL; HRESULT hRes = E_OUTOFMEMORY; //ATL::CComObject< CMath > *p = new ATL::CComObject< CMath > (pv); T1* p = new T1(pv)); //这里创建了组件或类厂 //..... hRes = p->QueryInterface(riid, ppv); //获取组件接口指针 return hRes; }}; 

到此，组件创建完成。

http://blog.csdn.net/hongjiqin/article/details/4460095