Redefinition of a class in C++

Question

I'm new to C++ and stuck in a problem with an Error, called

"Semantic Issue: Redefinition of 'B' cB.h".

I have two classes, A and B, where cA should handle an Object of cB by reference and one friend function of cA, fExample. This is what the code looks like:

.h file cA:

#include "cB.h"

class A{
  int val1, val2;
public:
  friend void fExample(int, cB &);
};

.h file cB:

class B{
  int val1, val2;
public:
  void set_val1(int);
};

.cpp file cB:

#include <iostream>
#include "cB.h"
using namespace std;

void B::set_val1(int tVal){
  val1 = tVal;
}

For me, it seems there is no way of working with the cB-object by reference with a friend function of cA. I would know some workarounds, but that's not my intention, I want to learn how to handle this problem the right way.

So thanks in advance for helping!

Sorry, there should be 'class B', not 'class cB'. i've miswritten it in the code above. — flaming.codes, Dec 02 '14 at 18:49
In the header file for a you do not need to include the header for b. Instead forward declare b. Also add include guards. — drescherjm, Dec 02 '14 at 18:53
http://stackoverflow.com/questions/21090041/why-include-guards — Drew Dormann, Dec 02 '14 at 18:54
I thought only pointers were allowed when using forward declaration? — flaming.codes, Dec 02 '14 at 18:54

score 1 · Accepted Answer · answered Dec 02 '14 at 18:54

1

This type of error often happen due to missing include guards. The Simplest way is:

#ifndef HEADER_NAME
#define HEADER_NAME

You may also use #pragma once

answered Dec 02 '14 at 18:54

deeiip

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While widely supported, `#pragma once` (like any other *pragma*) is non-standard, include guards are a better alternative. – outlyer Dec 02 '14 at 19:36

Redefinition of a class in C++

1 Answers1