用统一的一个结构管理动态创建

#define RUN_TIME(classname) (&classname::runtime)

#define DECLARE_DYNAMIC()
public:
static RUNTIME runtime;
virtual char *GetClassName();
virtual char *GetBaseClassName();
static CObject *MyCreate();

#define IMPLEMENT_DYNAMIC(theclass, baseclass)\

RUNTIME theclass::runtime = {#theclass, &baseclass::runtime, theclass::MyCreate};
char *theclass::GetClassName()
{
　　return theclass::runtime.classname;
}
char *theclass::GetBaseClassName()
{
　　return theclass::runtime.Baseruntime->classname;
}
CObject * theclass::MyCreate()
{
　　return new theclass;
}

typedef struct _RUNTIME

{

　　char *classname;

　　struct _RUNTIME *Baseruntime;

　　CObject *(*pfnCreate)();

　　CObject *Create();

}RUNTIME;

CObject * _RUNTIME::Create()

{

　　return new CObject;

}

宏替换：在预编译阶段，对我们源程序文本进行处理。动态创建机制，实际是一种预编译替换机制

编译阶段：我们的源程序将不再发生任何改变。