Question

Code:

#include<iostream>

using namespace std;

class MyClassOne;

class MyClassTwo
{
    int myInteger;
    float myFloat;

public:
    void SetData(int myIntegerParameter, float myFloatParameter)
    {
        myInteger = myIntegerParameter;
        myFloat = myFloatParameter;
    }
    void Show(MyClassOne myObjectParameter)
    {
        cout<<"MyClassOne..."<<"\n";
        cout<<myObjectParameter.myInteger<<"\n";
        cout<<myObjectParameter.myFloat<<"\n";

        cout<<"MyClassTwo..."<<"\n";
        cout<<myInteger<<"\n";
        cout<<myFloat<<"\n";
    }
};

class MyClassOne
{
    int myInteger;
    float myFloat;

public:
    void SetData(int myIntegerParameter, float myFloatParameter)
    {
        myInteger = myIntegerParameter;
        myFloat = myFloatParameter;
    }
    friend void MyClassTwo :: Show(MyClassOne);
};

int main()
{
    MyClassOne myObjectOne;
    myObjectOne.SetData(10, 10.5);

    MyClassTwo myObjectTwo;
    myObjectTwo.SetData(20, 20.5);

    myObjectTwo.Show(myObjectOne);

    return 0;
}

Error Message:

1>friend_function.cpp(22) : error C2027: use of undefined type 'MyClassOne'
1>friend_function.cpp(6) : see declaration of 'MyClassOne'
1>friend_function.cpp(22) : error C2228: left of '.myInteger' must have 

class/struct/union
1>friend_function.cpp(23) : error C2027: use of undefined type 'MyClassOne'
1>friend_function.cpp(6) : see declaration of 'MyClassOne'
1>friend_function.cpp(23) : error C2228: left of '.myFloat' must have 

class/struct/union
1>Generating Code...
1>Build log was saved at "file://Debug\BuildLog.htm"
1>Problem_05___Friend_Function - 4 error(s), 0 warning(s)
========== Rebuild All: 0 succeeded, 1 failed, 0 skipped ==========

Answer 1

MyClassTwo::Show expects a complete definition of MyClassOne.

Move the body of the Show method to after the definition of MyClassOne and it will work.