c++交叉#include问题

这个问题会引起莫名其妙的编译错误，

碰到类里有其他类的指针的话，不要#include，提前声明下即可

class_a.h

#ifndef CLASS_A_H
#define CLASS_A_H  

class B;
class A
{
public:
    void Print()
    {
        std::cout << "This is class A\n";
    }  

    B *b;
};  

#endif  

class_b.h

#ifndef CLASS_B_H
#define CLASS_B_H  

class A;
class B
{
public:
    void Print()
    {
        std::cout << "This is class B\n";
    }  

    A *a;
};  

#endif  

main.cpp

#include <iostream>  

#include "class_a.h"
#include "class_b.h"  

int main()
{
    A aa;
    aa.b->Print();  

    B bb;
    bb.a->Print();
}