接上篇http://www.cnblogs.com/Clingingboy/archive/2011/06/14/2081019.html

一.封装生命周期步骤

由于以上过程容易出错,所以在CComCreator 对其生命周期调用进行了封装

template <class T1>
class CComCreator
{
public:_Success_(return == S_OK) static HRESULT WINAPI CreateInstance(_In_opt_ void* pv, _In_ REFIID riid, _Deref_out_ LPVOID* ppv){ATLASSERT(ppv != NULL);if (ppv == NULL)return E_POINTER;*ppv = NULL;HRESULT hRes = E_OUTOFMEMORY;T1* p = NULL;ATLPREFAST_SUPPRESS(6014)/* prefast noise VSW 489981 */ATLTRY(p = new T1(pv))
ATLPREFAST_UNSUPPRESS()if (p != NULL){p->SetVoid(pv);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);if (hRes != S_OK)delete p;}return hRes;}
};

现在创建对象又简化了一些

class CPenguin : ... {
public:...typedef CComCreator<CComPolyObject<CPenguin> > _CreatorClass;
};
STDMETHODIMP CAviary::CreatePenguin(IBird** ppbird) {return CPenguin::_CreatorClass::CreateInstance(0,IID_IBird,(void**)ppbird);
}

二.使用CComCoClass 进一步简化

由于CreateInstance方法很常用,进一步简化就是继承一个既有封装好的类,就是CComCoClass,其实现方式是一样的

template <class T, const CLSID* pclsid = &CLSID_NULL>
class CComCoClass {
public:                                                         ...                                                         template <class Q>                                          static HRESULT CreateInstance(IUnknown* punkOuter, Q** pp) {return T::_CreatorClass::CreateInstance(punkOuter,      __uuidof(Q), (void**) pp);                          }                                                           template <class Q>                                          static HRESULT CreateInstance(Q** pp) {                     return T::_CreatorClass::CreateInstance(NULL,           __uuidof(Q), (void**) pp);                          }
};

三.用宏简化CComCreator的创建

#define DECLARE_POLY_AGGREGATABLE(x) public:\      typedef ATL::CComCreator< \                      ATL::CComPolyObject< x > > _CreatorClass;

现在简化成这样(或者将DECLARE_AGGREGATABLE放在CComCoClass内部)

class CPenguin : public CComCoClass<CPenguin, &CLSID_CPenguin> {
public:...DECLARE_AGGREGATABLE(CPenguin)
};

四.是否支持聚合(CComFailCreator)