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Understanding The COM Single-Threaded Apartment Part 1

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6 Jan 2005CPOL49 min read 841.3K   4.9K   442  
Learn the fundamental principles of the COM Single-Threaded Apartment Model by code examples.
#include "ExeObj01.h"
#include <stdio.h>






CExeObj01::CExeObj01()
{
}





CExeObj01::~CExeObj01()
{
}





STDMETHODIMP CExeObj01::QueryInterface(REFIID riid, void** ppvObject)
{
  if (riid == IID_IUnknown || riid == IID_IExeObj01)
  {
	*ppvObject = (IExeObj01*)this;
	((CReferenceCountedObject*)this) -> AddRef();
	return S_OK;
  }
  
  return E_NOINTERFACE;
}





// IUnknown method.
STDMETHODIMP_(ULONG) CExeObj01::AddRef()
{
  return CReferenceCountedObject::AddRef();
}





// IUnknown method.
STDMETHODIMP_(ULONG) CExeObj01::Release()
{
  return CReferenceCountedObject::Release();
}





STDMETHODIMP CExeObj01::TestMethod1()
{
  TCHAR szMessage[256];

  sprintf (szMessage, "0x%X", GetCurrentThreadId());

  ::MessageBox(NULL, szMessage, "CExeObj01::TestMethod1()", MB_OK);

  return S_OK;
}





CExeObj01_Factory::CExeObj01_Factory()
{
}





CExeObj01_Factory::~CExeObj01_Factory()
{
}





// IUnknown method. Overridde QueryInterface() method.
STDMETHODIMP CExeObj01_Factory::QueryInterface(REFIID riid, void** ppvObject)
{
  if (riid == IID_IUnknown)
  {
    CReferenceCountedObject* pCReferenceCountedObject = (CReferenceCountedObject*)this;

	*ppvObject = (IUnknown*)pCReferenceCountedObject;
	((CReferenceCountedObject*)this) -> AddRef();
	return S_OK;
  }

  if (riid == IID_IClassFactory)
  {
    *ppvObject = (IClassFactory*)this;
	((CReferenceCountedObject*)this) -> AddRef();
	return S_OK;
  }

  *ppvObject = NULL;
  
  return E_NOINTERFACE;
}





// IUnknown method.
STDMETHODIMP_(ULONG) CExeObj01_Factory::AddRef()
{
  return CClassFactory::AddRef();
}





// IUnknown method.
STDMETHODIMP_(ULONG) CExeObj01_Factory::Release()
{
  return CClassFactory::Release();
}





// IClassFactory method.
STDMETHODIMP CExeObj01_Factory::CreateInstance
(
  IUnknown __RPC_FAR *pUnkOuter,
  REFIID riid,
  void __RPC_FAR *__RPC_FAR *ppvObject
)
{
  CExeObj01* pCExeObj01 = NULL;

  // Initialise the receiver.
  *ppvObject = NULL;

  if (pUnkOuter != NULL)
  {
	return CLASS_E_NOAGGREGATION;
  }

  // Create an instance of the component.
  pCExeObj01 = new CExeObj01;

  if (pCExeObj01 == NULL)
  {
	return E_OUTOFMEMORY;
  }

  pCExeObj01 -> QueryInterface (riid, ppvObject);

  pCExeObj01 -> Release();

  return S_OK;
}





// IClassFactory method.
STDMETHODIMP CExeObj01_Factory::LockServer
(
  BOOL fLock
)
{
  return CClassFactory::LockServer(fLock);
}








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License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


Written By
Systems Engineer NEC
Singapore Singapore
Lim Bio Liong is a Specialist at a leading Software House in Singapore.

Bio has been in software development for over 10 years. He specialises in C/C++ programming and Windows software development.

Bio has also done device-driver development and enjoys low-level programming. Bio has recently picked up C# programming and has been researching in this area.

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