Dynamic Creation（动态创建）
DECLARE_DYNCREATE/IMPLEMENT_DYNCREATE宏
用于对象的动态创建，即从保存的文件中恢复原始对象。这2个宏在RTTI即DECLARE_DYNMICAL/IMPLEMENT_DYNAMIC宏的基础上添加了2个成员：
CObject* CreateObject();
static CRuntimeClass* PASCAL Load(CArchive& ar, UINT* pwSchemaNum);//static成员函数，属于类。
#define DECLARE_DYNCREATE(class_name) \
DECLARE_DYNAMIC(class_name) \
static CObject* PASCAL CreateObject();
#define IMPLEMENT_DYNCREATE(class_name, base_class_name) \
CObject* PASCAL class_name::CreateObject() \
{ return new class_name; } \
IMPLEMENT_RUNTIMECLASS(class_name, base_class_name, 0xFFFF, \
class_name::CreateObject, NULL)
#define IMPLEMENT_RUNTIMECLASS(class_name, base_class_name, wSchema, pfnNew, class_init) \
AFX_COMDAT const CRuntimeClass class_name::class##class_name = { \
#class_name, sizeof(class class_name), wSchema, pfnNew, \
RUNTIME_CLASS(base_class_name), NULL, class_init }; \
CRuntimeClass* class_name::GetRuntimeClass() const \
{ return RUNTIME_CLASS(class_name); } \
#define AFX_COMDAT __declspec(selectany)
#define RUNTIME_CLASS(class_name) _RUNTIME_CLASS(class_name)
#define _RUNTIME_CLASS(class_name) ((CRuntimeClass*)(&class_name::class##class_name))
CreateObject函数生成对象，若为抽象类，则返回NULL，否则new一个对象
如下是使用：
void main()
{
...
//Test Dynamic Creation
CRuntimeClass* pClassRef;
CObject* pOb;
while(1)
{
if((pClassRef = CRuntimeClass::Load())==NULL)
break;
pOb = pClassRef->CreateObject();
if(pOb != NULL)
pOb->SayHello();
}
}
CObject* CRuntimeClass::CreateObject()
{
if(m_pfnCreateObject == NULL)
{
...
}
CObject* pObject = NULL;
pObject = (*m_pfnCreateObject)();
return pOjbect;
}
CRuntimeClass* PASCAL CRuntimeClass::Load()
{
char szClassName[64];
CRuntimeClass* pClass;
cout << "enter a class name: ";
cin >> szClassName;
for(pClass = pFirstClass; pClass != NULL; pClass = pClass->m_pNextClass)
{
if(strcmp(szClassName,pClass->m_lpszClassName) == 0)
return pClass;
}
...
}