Question

this maybe a little trivial but I’m puzzled with such problem.

I want to create two classes Class1, Class2. Both classes should contain a field that contains pointer to instance of the other class. So they should be cross linked.

If I do it like this then I get an error from the compiller saying:
– ISO C++ forbids declaration of ‘Class1’ with no type
– expected ‘;’ before * token

Please help 🙂

file: class1.h

#ifndef CLASS1_H
#define CLASS1_H

#include "class2.h"

class Class1 {
public:
    Class1();
private:
    Class2* link;
}

#endif

file: class2.h

#ifndef CLASS2_H
#define CLASS2_H

#include "class1.h"

class Class2 {
public:
    Class2();
private:
    Class1* link;
}

#endif

Answer 1

Add class declaration (as opposed to definition) before you use it. For example, you could have:

#ifndef CLASS1_H
#define CLASS1_H

class Class2;

class Class1
{
public:
    Class1();
private:
    Class2* link;
}

#endif

and do the same for Class2.h.