Question

为什么CRuntimeClass结构里包含有CObject CObject也包含有CRuntimeClass

怎么能相互包含能 后声明的才能包含先声明的吧 怎么可能同时包含

Answer 1

========>《深入浅出MFC》侯捷P96页
R:\DISSECT\FRAME3.03>my.exe
CView
4
65535
CDocument
4
65535
CFrameWnd
4
65535
CWnd
4
65535
CWinApp
12
65535
CWinThread
4
65535
CCmdTarget
4
65535
CObject
4
65535
<=======================================
////////////////////////--------------CRuntimeClass-------------------------///////////////////////////
// Basic object model

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
#ifdef _AFXDLL
CRuntimeClass* (PASCAL* m_pfnGetBaseClass)();
#else
CRuntimeClass* m_pBaseClass;
#endif

// Operations
CObject* CreateObject();
BOOL IsDerivedFrom(const CRuntimeClass* pBaseClass) const;

// Implementation
void Store(CArchive& ar) const;
static CRuntimeClass* PASCAL Load(CArchive& ar, UINT* pwSchemaNum);

// CRuntimeClass objects linked together in simple list
CRuntimeClass* m_pNextClass; // linked list of registered classes
};
====================================================================
///////////////////////////----------------CObject---------------------///////////////////////////////
// class CObject is the root of all compliant objects

#ifdef _AFXDLL
class CObject
#else
class AFX_NOVTABLE CObject
#endif
{
public:

// Object model (types, destruction, allocation)
virtual CRuntimeClass* GetRuntimeClass() const;
virtual ~CObject(); // virtual destructors are necessary

// Diagnostic allocations
void* PASCAL operator new(size_t nSize);
void* PASCAL operator new(size_t, void* p);
void PASCAL operator delete(void* p);
#if _MSC_VER >= 1200
void PASCAL operator delete(void* p, void* pPlace);
#endif

#if defined(_DEBUG) && !defined(_AFX_NO_DEBUG_CRT)
// for file name/line number tracking using DEBUG_NEW
void* PASCAL operator new(size_t nSize, LPCSTR lpszFileName, int nLine);
#if _MSC_VER >= 1200
void PASCAL operator delete(void *p, LPCSTR lpszFileName, int nLine);
#endif
#endif

// Disable the copy constructor and assignment by default so you will get
// compiler errors instead of unexpected behaviour if you pass objects
// by value or assign objects.
protected:
CObject();
private:
CObject(const CObject& objectSrc); // no implementation
void operator=(const CObject& objectSrc); // no implementation

// Attributes
public:
BOOL IsSerializable() const;
BOOL IsKindOf(const CRuntimeClass* pClass) const;

// Overridables
virtual void Serialize(CArchive& ar);

#if defined(_DEBUG) || defined(_AFXDLL)
// Diagnostic Support
virtual void AssertValid() const;
virtual void Dump(CDumpContext& dc) const;
#endif

// Implementation
public:
static const AFX_DATA CRuntimeClass classCObject;
#ifdef _AFXDLL
static CRuntimeClass* PASCAL _GetBaseClass();
#endif
};