COM创建对象方法

软件架构师何志丹

1、创建COM组件的框架。(组件已注册)

IUnknown *pUnk = NULL;

IObject *pObject = NULL;

CoInitialize(NULL);

CoCreateInstance(CLSID_Object, CLSCTX_INPROC_SERVER, NULL, IDD_Unknown, (void**)&pUnk);

pUnk->QueryInterface(IID_IObject, (void**)&pObject);

pUnk->Release();

pObject->Func();

pObject->Release();
CoUninitialize();

CoCreateInstance的内部:

CoCreateInstance(....)
{
　　.......
　　IClassFactory *pClassFactory=NULL;

//先获得类工厂对象①
　　CoGetClassObject(CLSID_Object, CLSCTX_INPROC_SERVER, NULL, IID_IClassFactory, (void **)&pClassFactory);

//再通过类工厂对象创建组件并且得到IUnknown指针。②
　　pClassFactory->CreateInstance(NULL, IID_IUnknown, (void**)&pUnk);
　　pClassFactory->Release();
　　........
}

//①-------------------

CoGetClassObject的内部:

CoGetClassObject(.....)
{
　　//通过查注册表CLSID_Object，得知组件DLL的位置、文件名
　　//使用LoadLibrary装入DLL库
　　//使用函数GetProcAddress( "DllGetClassObject" )得到DLL库中函数DllGetClassObject的函数指针。
　　//调用DllGetClassObject
}

DllGetClassObject是用来获得类工厂对象的，只有先得到类工厂才能去创建组件。

DllGetClassObject代码:
HRESULT_export PASCAL DllGetClassObject (REFCLSID rclsid, REFIID riid, LPVOID * ppvObj)
{
    HRESULT hr = E_OUTOFMEMORY;
    *ppvObj = NULL;

    CClassFactory *pClassFactory = new CClassFactory(rclsid); //类工厂
    if (pClassFactory != NULL)   {
        hr = pClassFactory->QueryInterface(riid, ppvObj);
        pClassFactory->Release();
    }
    return hr;
}

//②----------------

CFactory::CreateInstance(.....)
{
　　...........
　　CObject *pObject = new CObject; //组件对象
　　pObject->QueryInterface(IID_IUnknown, (void**)&pUnk);
　　pObject->Release();
　　...........
}

实例：

CComPtr<IAVIer> m_piAVIer;

m_piAVIer.CoCreateInstance(L"AVI.AVIer");

2、通过LoadLibrary和DllGetClassObject创建组件对象（组件未注册)

CComPtr<IAVIer> m_piAVIer;

typedef int (WINAPI *DllGetClassObjectPtr)(REFCLSID, REFIID, LPVOID*);

HMODULE hModule = LoadLibrary(dll文件路径);

//得到DllGetClassObject函数地址

DllGetClassObjectPtr ProcPtr = (DllGetClassObjectPtr)GetProcAddress(hModule, "DllGetClassObject");

CLSID rclsid;
IID riid;
::CLSIDFromString(A2W("{D5A365A3-44F8-47A0-8FCF-062372B1EB83}"), &rclsid);//类ID
::IIDFromString(A2W("{BE136856-CBEA-4079-A02B-BBC7A382BDB3}"), &riid);//接口ID

IClassFactory *pICF = NULL;//类工厂接口指针

ProcPtr(rclsid, IID_IClassFactory, (void**)(&pICF));//获取类工厂接口指针

//以上相当于①

pICF->CreateInstance(NULL, riid, (void**)&m_piAVIer);//创建COM对象

//以上相当于②

pICF->Release();

备注:

AVIer.rgs文件

HKCR
{
Avi.AVIer.1 = s 'AVIer Class'
{
  CLSID = s '{D5A365A3-44F8-47A0-8FCF-062372B1EB83}'
}
Avi.AVIer = s 'AVIer Class'
{
  CLSID = s '{D5A365A3-44F8-47A0-8FCF-062372B1EB83}'
  CurVer = s 'Avi.AVIer.1'
}
NoRemove CLSID
{
  ForceRemove {D5A365A3-44F8-47A0-8FCF-062372B1EB83} = s 'AVIer Class'
  {
   ProgID = s 'Avi.AVIer.1'
   VersionIndependentProgID = s 'Avi.AVIer'
   ForceRemove 'Programmable'
   InprocServer32 = s '%MODULE%'
   {
    val ThreadingModel = s 'Both'
   }
   'TypeLib' = s '{59AE79C3-3AC6-42E1-ABED-10B363EDAA4C}'
  }
}
}