MFC中的运行时类型识别(RTTI)

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MFC中的运行时类型识别(RTTI)

2024-10-20 18:55:02 213人阅读

RTTI是Runtime Type Identification的缩写，中文名为“运行时类型识别”。

MFC早在编译器支持RTTI之前，就有了这种能力。我们现在要以相同的手法，在Console程序中仿真出来。我希望我的类库具备IsKindOf 的能力，能在执行期侦测到某个对象是否属于某个类，并传回TRUE 或 FALSE。以形状 Shape为例，我希望：

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即长方形属于“长方形类”，正方形属于“长方形类”，圆不属于“长方形类”，原因是长方形派生正方形类。

CMyDoc 属于“CMyDoc类”，CMyDoc也属于“CDocument类”，CMyDoc也属于“CCmdTarget类” ，CMyDoc不属于“CWnd类” 。原因是CCmdTarget派生CDocument类，CDocument派生 CMyDoc类。

同时，我希望，每一个类都能拥有这样一个CRuntimeClass 成员变量，并且最后有一定的命名规则（例如，在类名称之前冠以“class”作为它的名称），然后，经由某种手段将整个类库构建好之后，“类别型录”就能呈现如下图（2）所示的面貌：

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图（2）“类别型录”的链表形式

下面，以控制台应用程序Frame3为例，模拟mfc的RTTI功能。

在案例Frame3 的cpp 文件中，有这样的操作：

IMPLEMENT_DYNAMIC(CCmdTarget,CObject)
IMPLEMENT_DYNAMIC(CWinThread,CCmdTarget)
IMPLEMENT_DYNAMIC(CWinApp,CWinThread)
IMPLEMENT_DYNAMIC(CWnd,CCmdTarget) //其实在MFC中此句是,IMPLEMENT_DYNCREATE()
IMPLEMENT_DYNAMIC(CFrameWnd,CWnd)  //其实在MFC中此句是,IMPLEMENT_DYNCREATE()
IMPLEMENT_DYNAMIC(CDocument,CCmdTarget)
IMPLEMENT_DYNAMIC(CView,CWnd)

于是，组织出如图（3-1）所示的一张大网：

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为了证明，程序中存在整个“类别型录网”。我在main函数中调用 PrintAllClasses ，把链表中的每一个元素的类名称、对象大小，以及scheme.no，打印出来。

void PrintAllClasses() //输出“类别型录网“
{
	CRuntimeClass* pClass;

	//just walk through the simple list of registered classes
	for(pClass = CRuntimeClass::pFirstClass; pClass!=NULL;
			pClass = pClass->m_pNextClass)
	{
		cout<<pClass->m_lpszClassName<<"\n";
		cout<<pClass->m_nObjectSize<<"\n";
		cout<<pClass->m_wSchema<<"\n";
	}
}

效果如下：

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图（4）链表中的每一个元素的类名称、对象大小，以及scheme.no，说明存在该“类别型录网”

详细代码如下：

//mfc.h

#define BOOL int
#define TRUE 1
#define FALSE 0
#define LPCSTR  LPSTR
typedef char*   LPSTR;
#define UINT int
#define PASCAL _stdcall

#include <iostream.h>

class CObject;

struct CRuntimeClass
{
// Attributes
        LPCSTR m_lpszClassName;
        int m_nObjectSize;
        UINT m_wSchema; // schema number of the loaded class
        CObject* (PASCAL* m_pfnCreateObject)(); // NULL => abstract class
        CRuntimeClass* m_pBaseClass;

        // CRuntimeClass objects linked together in simple list
        static CRuntimeClass* pFirstClass; // start of class list
        CRuntimeClass* m_pNextClass;       // linked list of registered classes
};

struct AFX_CLASSINIT
        { AFX_CLASSINIT(CRuntimeClass* pNewClass); };

#define RUNTIME_CLASS(class_name)         (&class_name::class##class_name)

#define DECLARE_DYNAMIC(class_name) public:         static CRuntimeClass class##class_name;         virtual CRuntimeClass* GetRuntimeClass() const;

#define _IMPLEMENT_RUNTIMECLASS(class_name, base_class_name, wSchema, pfnNew)         static char _lpsz##class_name[] = #class_name;         CRuntimeClass class_name::class##class_name = {                 _lpsz##class_name, sizeof(class_name), wSchema, pfnNew,                         RUNTIME_CLASS(base_class_name), NULL };         static AFX_CLASSINIT _init_##class_name(&class_name::class##class_name);         CRuntimeClass* class_name::GetRuntimeClass() const                 { return &class_name::class##class_name; } 
#define IMPLEMENT_DYNAMIC(class_name, base_class_name)         _IMPLEMENT_RUNTIMECLASS(class_name, base_class_name, 0xFFFF, NULL)

class CObject
{
public:
  CObject::CObject()  {
                      }
  CObject::~CObject() {
                      }

  virtual CRuntimeClass* GetRuntimeClass() const;

public:
  static CRuntimeClass classCObject;
};

class CCmdTarget : public CObject
{
        DECLARE_DYNAMIC(CCmdTarget)
public:
  CCmdTarget::CCmdTarget()  {
                            }
  CCmdTarget::~CCmdTarget() {
                            }
};

class CWinThread : public CCmdTarget
{
        DECLARE_DYNAMIC(CWinThread)
public:
  CWinThread::CWinThread()  {
                            }
  CWinThread::~CWinThread() {
                            }

  virtual BOOL InitInstance() {
                                return TRUE;
                              }
  virtual int Run() {
                      return 1;
                    }
};

class CWnd;

class CWinApp : public CWinThread
{
        DECLARE_DYNAMIC(CWinApp)
public:
  CWinApp* m_pCurrentWinApp;
  CWnd* m_pMainWnd;

public:
  CWinApp::CWinApp()  {
                        m_pCurrentWinApp = this;
                      }
  CWinApp::~CWinApp() {
                      }

  virtual BOOL InitApplication() {
                                   return TRUE;
                                 }
  virtual BOOL InitInstance()    {
                                   return TRUE;
                                 }
  virtual int Run() {
                      return CWinThread::Run();
                    }
};

class CDocument : public CCmdTarget
{
        DECLARE_DYNAMIC(CDocument)
public:
  CDocument::CDocument()   {
                           }
  CDocument::~CDocument()  {
                           }
};

class CWnd : public CCmdTarget
{
        DECLARE_DYNAMIC(CWnd)
public:
  CWnd::CWnd()   {
                 }
  CWnd::~CWnd()  {
                 }

  virtual BOOL Create();
  BOOL CreateEx();
  virtual BOOL PreCreateWindow();
};

class CFrameWnd : public CWnd
{
        DECLARE_DYNAMIC(CFrameWnd)
public:
  CFrameWnd::CFrameWnd()   {
                           }
  CFrameWnd::~CFrameWnd()  {
                           }
  BOOL Create();
  virtual BOOL PreCreateWindow();
};

class CView : public CWnd
{
        DECLARE_DYNAMIC(CView)
public:
  CView::CView()   {
                   }
  CView::~CView()  {
                   }
};


// global function
CWinApp* AfxGetApp();

//mfc.cpp

#include "my.h"

CMyWinApp theApp;

BOOL CMyWinApp::InitInstance()
{
	m_pMainWnd = new CMyFrameWnd;
	return TRUE;
}

CMyFrameWnd::CMyFrameWnd()
{
	Create();
}

void PrintAllClasses() //输出“类别型录网“
{
	CRuntimeClass* pClass;

	//just walk through the simple list of registered classes
	for(pClass = CRuntimeClass::pFirstClass; pClass!=NULL;
			pClass = pClass->m_pNextClass)
	{
		cout<<pClass->m_lpszClassName<<"\n";
		cout<<pClass->m_nObjectSize<<"\n";
		cout<<pClass->m_wSchema<<"\n";
	}
}

void main()
{
	CWinApp* pApp = AfxGetApp();

	pApp->InitApplication();
	pApp->InitInstance();
	pApp->Run();

	PrintAllClasses();
}

//my.h

#include <iostream.h>
#include "mfc.h"

class CMyWinApp:public CWinApp
{
public:
	CMyWinApp::CMyWinApp(){}
	CMyWinApp::~CMyWinApp(){}

	virtual BOOL InitInstance();
};

class CMyFrameWnd:public CFrameWnd
{
public:
	CMyFrameWnd();
	~CMyFrameWnd(){}
};

class CMyDoc:public CDocument
{
public:
	CMyDoc::CMyDoc(){}
	CMyDoc::~CMyDoc(){}
};

class CMyView:public CView
{
public:
	CMyView::CMyView(){}
	CMyView::~CMyView(){}
};

//global function
void PrintAllClasses();

//my.cpp

#include "my.h"

CMyWinApp theApp;

BOOL CMyWinApp::InitInstance()
{
	m_pMainWnd = new CMyFrameWnd;
	return TRUE;
}

CMyFrameWnd::CMyFrameWnd()
{
	Create();
}

void PrintAllClasses() //输出“类别型录网“
{
	CRuntimeClass* pClass;

	//just walk through the simple list of registered classes
	for(pClass = CRuntimeClass::pFirstClass; pClass!=NULL;
			pClass = pClass->m_pNextClass)
	{
		cout<<pClass->m_lpszClassName<<"\n";
		cout<<pClass->m_nObjectSize<<"\n";
		cout<<pClass->m_wSchema<<"\n";
	}
}

void main()
{
	CWinApp* pApp = AfxGetApp();

	pApp->InitApplication();
	pApp->InitInstance();
	pApp->Run();

	PrintAllClasses();
}

MFC中的运行时类型识别(RTTI)

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MFC中的运行时类型识别(RTTI)

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