Thread: confused with friend function

Inside FileTwo.h

Code:

#ifndef FILETWO#define FILETWO#include"FileOne.h"class FileOne ;class FileTwo{public:    int Test(FileOne One){        return (One.var1+One.var2);}    FileTwo(void);    ~FileTwo(void);};#endif

Inside FileOne.h

Code:

#ifndef FILEONE#define FILEONE#include"FileTwo.h"class FileTwo ;class FileOne{private:     int var1 , var2 , var3 ;public :    friend int FileTwo::Test(FileOne One);    FileOne(){        var1= 12;var2 = 24;    }};#endif

Inside main.cpp

Code:

#include<iostream>using namespace std ;#include"FileOne.h"#include"FileTwo.h"int main(){FileOne one ;FileTo two ;cout<<two.Test(one);}

During compilation i got the following error

Code:

 1-- error C2027: use of undefined type 'FileOne' c:\users\e543925\documents\visual studio 2005\projects\myproject\filetwo.h   2--error C2027: use of undefined type 'FileOne'  c:\users\e543925\documents\visual studio 2005\projects\myproject\filetwo.h     3--error C2228: left of '.var1' must have class/struct/union c:\users\e543925\documents\visual studio 2005\projects\myproject\filetwo.h   4--error C2228: left of '.var2' must have class/struct/union c:\users\e543925\documents\visual studio 2005\projects\myproject\filetwo.h

I have found one workaround like definning the Test function inside FileTwo.cpp . But i want to know how the above issue can be resolved inside header file .