COM 学习（四）

还只是模拟，把组件 抽取出来，通过DLL的方式调用

1.定义接口

//
// Iface.h
//

// Interfaces
interface IX : IUnknown
{
	virtual void __stdcall Fx() = 0 ;
} ;

interface IY : IUnknown
{
	virtual void __stdcall Fy() = 0 ;
} ;

interface IZ : IUnknown
{
	virtual void __stdcall Fz() = 0 ;
} ;

// Forward references for GUIDs
extern "C"
{
	extern const IID IID_IX ;
	extern const IID IID_IY ;
	extern const IID IID_IZ ;
}

2. 定义 IID，接口标志

//
// GUIDs.cpp - Interface IDs
//
#include <objbase.h>

extern "C" 
{
	// {32bb8320-b41b-11cf-a6bb-0080c7b2d682}
	extern const IID IID_IX = 
		{0x32bb8320, 0xb41b, 0x11cf,
		{0xa6, 0xbb, 0x0, 0x80, 0xc7, 0xb2, 0xd6, 0x82}} ;

	// {32bb8321-b41b-11cf-a6bb-0080c7b2d682}
	extern const IID IID_IY = 
		{0x32bb8321, 0xb41b, 0x11cf,
		{0xa6, 0xbb, 0x0, 0x80, 0xc7, 0xb2, 0xd6, 0x82}} ;

	// {32bb8322-b41b-11cf-a6bb-0080c7b2d682}
	extern const IID IID_IZ = 
		{0x32bb8322, 0xb41b, 0x11cf,
		{0xa6, 0xbb, 0x0, 0x80, 0xc7, 0xb2, 0xd6, 0x82}} ;

	// The extern is required to allocate memory for C++ constants.
}

3. 通过 组件名，创建组件，返回IUnknown指针,模拟了 实际COM中的CoCreateInstance

//
// Create.h
//

IUnknown* CallCreateInstance(char* name) ;

//
// Create.cpp 
//
#include <iostream>
#include <unknwn.h>    // Declare IUnknown.

#include "Create.h"
using namespace std;
typedef IUnknown* (*CREATEFUNCPTR)() ;

IUnknown* CallCreateInstance(char* name)
{
	// Load dynamic link library into process.
	HINSTANCE hComponent = ::LoadLibrary(name) ;
	if (hComponent == NULL)
	{
		cout << "CallCreateInstance:\tError: Cannot load component." << endl ;
		return NULL ;
	}

	// Get address for CreateInstance function.
	CREATEFUNCPTR CreateInstance 
		= (CREATEFUNCPTR)::GetProcAddress(hComponent, "CreateInstance") ;
	if (CreateInstance == NULL)
	{
		cout  << "CallCreateInstance:\tError: "
		      << "Cannot find CreateInstance function."
		      << endl ;
		return NULL ;
	}

	return CreateInstance() ;
}

4. 客户端//

// Client1.cpp
// To compile, use: cl Client1.cpp Create.cpp GUIDs.cpp UUID.lib
//
#include <iostream>
#include <objbase.h>

#include "Iface.h"
#include "Create.h"
using namespace std;

void trace(const char* msg) { cout << "Client 1:\t" << msg << endl ;}

//
// Client1
//
int main()
{
	HRESULT hr ;

	// Get the name of the component to use.
	char name[40] ;
	cout << "Enter the filename of a component to use [Cmpnt?.dll]: " ;
	cin  >> name ;
	cout << endl ;

	// Create component by calling the CreateInstance function in the DLL.
	trace("Get an IUnknown pointer.") ;
	IUnknown* pIUnknown = CallCreateInstance(name) ; 
	if (pIUnknown == NULL)
	{
		trace("CallCreateInstance Failed.") ;
		return 1 ;
	}

	trace("Get interface IX.") ;

	IX* pIX ; 
	hr = pIUnknown->QueryInterface(IID_IX, (void**)&pIX) ;

	if (SUCCEEDED(hr))
	{
		trace("Succeeded getting IX.") ;
		pIX->Fx() ;          // Use interface IX.
		pIX->Release() ;
	}
	else
	{
		trace("Could not get interface IX.") ;
	}

	trace("Release IUnknown interface.") ;
	pIUnknown->Release() ;
	system("pause");
	return 0 ;
}

5. 省略了 组件 定义、编译
对于CMPNT1.CPP和CMPNT1.DEF，通过nmake 命令，编译成 CMPNT1.dll 动态链接库
放入 客户端文件夹下，即可调用