方法1：

类的头文件中写

#pragma once
class MyTeacher
{
public:
	MyTeacher();
	~MyTeacher();
};

方法2：

类的头文件中写

#ifndef _MYTEACHER_H_
#define _MYTEACHER_H_

class MyTeacher
{
public:
	MyTeacher();
	~MyTeacher();
};
#endif