RTTI ---- Imitate from Inside MFC

最新推荐文章于 2023-08-09 00:15:26 发布

原创最新推荐文章于 2023-08-09 00:15:26 发布 · 1k 阅读

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#class #pascal #null #compiler #struct #mfc

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本文详细介绍了RTTI（运行时类型信息）机制的工作原理及其在MFC中的实现方式。通过具体的结构体CRuntimeClass定义和宏的使用，展示了如何在C++中实现对象类型的动态检查与构造。此外还提供了一种通过IsKindOf函数来判断对象继承关系的方法。

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RTTI means Runtime Type Information.
The compiler itself enable this functionality.

Now here just to imitate the mechalism referring to Inside MFC.

1. CRuntimeClass node to construct the link list.

struct CRuntimeClass
{
    LPCSTR                         m_lpszClassName;
    int                                     m_nObjectSize;
    UINT                                m_wSchema;
    CObject*                         (PASCAL* m_pfnCreateObject)();
    CRuntimeClass*         m_pBaseClass;
    CRuntimeClass*         m_pNextClass;

    static CRuntimeClass*   pFirstClass;
}

2. DECLARE_DYNAMIC(class_Name) to declare in .h file.

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

3. Implement macro in .cpp file

#define IMPLEMENT_DYNAMIC(class_name, base_class_name) /
               _IMPLEMENT_RUNTIMECLASS(class_name, base_class_name, 0xFFFF, NULL)

#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), wShema,pfnNew, /
                RuntimeClass(base_class_name),NULL }; /
                static AFX_CLASSINIT _init_##class_name(&class_name::class##class_name); /
                CRuntimeClass* class_name::GetRuntimeClass() const /
                {return &clas_name::class##class_name; }

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

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

3. The root class CObject has the specific definition as its m_pBaseClass = NULL.

4. Initialize the static variable.
   CRuntimeClass* CRuntimeClass::pFirstClass = NULL;

5. Initial Class to link all the nodes.
   AFX_CLASSINIT::AFX_CLASSINIT(CRuntimeClass* pNewClass)
{
       pNewClass->m_pNextClass = CRuntimeClass::pFirstClass;
       CRuntimeClass::pFirstClass = pNewClass;
}

6. Define the judge function in CObject IsKindof()
    BOOL CObject:: IsKindOf(const CRuntimeClass* pClass) const
{
       CRuntimeClass* pClassThis = GetRuntimeClass();
      while (pClassThis != null)
    {
          if (pClassThis == pClass)
             return True;
          pClassThis = pClassThis->m_pBaseClass;
    }
     return FALSE;
}