www.pudn.com > COMProgrammingExample.rar > README.WZD

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// How to use the COM object. 
///////////////////////////////////////////////////////////////////// 
1) The client should call the following to initialize the COM DLL from 
   the main process _and_ from any thread that will be using COM: 
 
	::CoInitializeEx( 
		NULL,				//always NULL 
		COINIT_APARTMENTTHREADED	//see book about threading models 
		); 
 
	NOTE: You also need to add _WIN32_DCOM to your project settings under  
	"Preprocessor definitions" in order to get the prototype definition for 
	::CoInitializeEx() included in your compile. 
 
2) Create a guids.h file that contains the class and interface ID's of 
   the COM classes you want to create. You can find these in the *_i.c 
   file generated by the MIDL compiler: 
 
#if !defined guids_h 
#define guids_h 
 
const IID CLSID_IWzdSrv = { 0x4487d432, 0xa6ff, 0x11d3, 0xa3, 0x98, 0x0, 0xc0, 0x4f, 0x57, 0xe, 0x2c }; 
const IID IID_IWzd = {0xC177116E,0x9AAA,0x11D3,{0x80,0x5D,0x00,0x00,0x00,0x00,0x00,0x00}}; 
 
#endif  
 
 
3) Include this guids.h file as well as the COM class's .h file (also generated by MIDL) and 
   an MFC .h file: 
 
#include "IServer\IWzd.h" 
#include "guids.h" 
#include  
 
4) To create a COM object one at a time, use: 
 
	IWzd *iWzd=NULL; 
	HRESULT hr=::CoCreateInstance( 
				CLSID_IWzdSrv,		// name of dll to load 
				NULL,				// aggregated COM object (none) 
				CLSCTX_INPROC_SERVER,// use dll 
				IID_IWzd,			// class to create and object of 
				(LPVOID*) &iWzd);	// returned object pointer 
	if (FAILED(hr)) 
	{ 
		_com_error err(hr); 
		AfxMessageBox(err.ErrorMessage()); 
		return; 
	} 
	iWzd->Release(); 
 
5) To call what CoCreateInstance() calls directly for diagnostic reasons, use: 
 
	// load DLL/EXE and get a pointer to its class factory 
	IClassFactory *pCF=NULL; 
	hr=::CoGetClassObject( 
				CLSID_IWzdSrv,		// name of dll to load 
				CLSCTX_INPROC_SERVER,// use dll 
				NULL,				// for DCOM, a COSERVERINFO structure that id's the remote server 
									// more typically set using OLEView 
				IID_IClassFactory,	// the class factory interface (all COM DLL/EXE's must have this interface) 
				(LPVOID*)&pCF);  
	if (FAILED(hr)) 
	{ 
		_com_error err(hr); 
		AfxMessageBox(err.ErrorMessage()); 
		return; 
	} 
	// ask class factory to creat the class 
	hr = pCF->CreateInstance( 
				NULL,				// aggregated COM object (none) 
				IID_IWzd,			// class to create and object of 
				(LPVOID*) &iWzd);	// returned object pointer 
	if (FAILED(hr)) 
	{ 
		_com_error err(hr); 
		AfxMessageBox(err.ErrorMessage()); 
		return; 
	} 
	pCF->Release();  
	iWzd->Release();  
 
6) To create multiple COM objects at once use: 
  
	// setup MULTI_QI structure with all the classes to create 
	MULTI_QI results[3]; 
	memset(results,0,sizeof(results)); 
	results[0].pIID=&IID_IWzd;	// class to create  
	results[1].pIID=&IID_IWzd;	 
	results[2].pIID=&IID_IWzd;	 
 
	// make the call 
	hr =::CoCreateInstanceEx( 
				CLSID_IWzdSrv,		// name of dll to load 
				NULL,				// aggregated COM object (none) 
				CLSCTX_INPROC_SERVER,// use dll 
				NULL,				// for DCOM, a COSERVERINFO structure that id's the remote server 
									// more typically set using OLEView 
				3,					// number of MULTI_QI structures in results 
				(MULTI_QI*)&results); // array of MULTI_QI structures 
	if (FAILED(hr)) 
	{ 
		_com_error err(hr); 
		AfxMessageBox(err.ErrorMessage()); 
		return; 
	} 
	for (int i=0;i<3;i++) 
	{ 
		if (FAILED(results[i].hr)) 
		{ 
			_com_error err(hr); 
			AfxMessageBox(err.ErrorMessage()); 
		} 
	} 
	IWzd *iWzd1=(IWzd*)results[0].pItf; 
	IWzd *iWzd2=(IWzd*)results[1].pItf; 
	IWzd *iWzd3=(IWzd*)results[2].pItf; 
	iWzd1->Release(); 
	iWzd2->Release(); 
	iWzd3->Release(); 
 
 
///////////////////////////////////////////////////////////////////// 
// From: COM Programming by Example by John E. Swanke 
// Copyright (C) 2000 jeswanke. All rights reserved. 
/////////////////////////////////////////////////////////////////////