Question

I am trying to make a class that contains two other objects, and those object should maintain a pointer to the class they are contained in. For

For example… (I am only using on object instance variable, in the final imagine there is a class very similar to ClassB)

This is just my main.cpp, figured I would include it to be thorough…

//Filename: main.cpp
#include "ClassA.hpp"

int main(int argc, char **args) {
    ClassA *a = new ClassA();
    // There would be some more here in the real code
    return 0;
}

Now for the classes in questions….

//Filename: classA.hpp
#ifndef CLASSA_H
#define CLASSA_H

#include "ClassB.hpp"

class ClassA {
public:
    ClassA() {
        b = new B(this);
    };
    virtual ~ClassA();

private:
    ClassB *b;
};

#endif //CLASSA_H

Now here is the other file…

#ifndef CLASSB_H
#define CLASSB_H

#include "ClassB.hpp"

//Filename: classB.hpp
class ClassB {
public:
    ClassB(ClassA *parent) {
        this->parent = parent;
    };
    virtual ~ClassB();
private:
    A *parent;
};

#endif //CLASSB_H

When I try to compile this, I am getting the error “error: ClassA does not name a type” and then of course “error: expected ‘)’ before ‘*’ token”
My guess is this has something to with them including one another?

(Not sure if it matters, but in the actual code, the function implementations are in a .cpp file that includes the header. Would that do it?)

Answer 1

Add

class ClassA;

before ClassB definition;
Simple example:

class B;

class A {
        B * b;
};

class B {
        A * a;
};

int main(int argc, char ** argv) {
        return 0;
}