How to create a header file to show the code "#if !defined(AFX_PLANE...."?

lanmuxu010

How can these codes appear on the header file?
#if !defined(AFX_PLANE_H__B446A8BD_83A8_489F_9874_9612567D1A37__INCLUDED_)
#define AFX_PLANE_H__B446A8BD_83A8_489F_9874_9612567D1A37__INCLUDED_

kanubis

This is automatically added by MFC, you can add it yourself
#if !define AAA
#define AAA

#endif

zhoudaj

First of all, we must clarify the meaning of adding these two lines of code
It is to avoid duplication of function definitions caused when the header file is included multiple times
If you use VC to automatically add classes, the system will automatically generate these codes
If you write the header file yourself, adding one yourself will have the same effect
For example, add in test.h
#ifndef TEST_H
#define TEST_H
.....
#endif