Building simple function to inherit 3 classes in C++

Question

I have created 3 classes - GrandMother, Mother and Daughter. I wrote a code such that the Daughter class inherits from the Mother class and the Mother class inherits from the GrandMother calss.

GrandMother.h :-

#ifndef GRANDMOTHER_H
#define GRANDMOTHER_H


class GrandMother
{
    public:
        GrandMother();
        ~GrandMother();
};

#endif // GRANDMOTHER_H

Mother.h :-

#ifndef MOTHER_H
#define MOTHER_H


class Mother: public GrandMother
{
    public:
        Mother();
        ~Mother();
};

#endif // MOTHER_H

Daughter.h :-

#ifndef DAUGHTER_H
#define DAUGHTER_H


class Daughter: public Mother
{
    public:
        Daughter();
        ~Daughter();
};

#endif // DAUGHTER_H

GrandMother.cpp :-

#include<iostream>
#include "Mother.h"
#include "Daughter.h"
#include "GrandMother.h"
using namespace std;

GrandMother::GrandMother()
{
    cout << "Grand Mother Constructor!!" << endl;
}

GrandMother::~GrandMother()
{
    cout << "Grand Mother Deconstroctor" << endl;
}

Mother.cpp :-

#include<iostream>
#include "Mother.h"
#include "Daughter.h"
#include "GrandMother.h"
using namespace std;

Mother::Mother()
{
    cout << "Mother Constructor!!" << endl;
}

Mother::~Mother()
{
    cout << "Mother Deconstroctor" << endl;
}

Daughter.cpp:-

#include<iostream>
#include "Mother.h"
#include "Daughter.h"
#include "GrandMother.h"
using namespace std;

Daughter::Daughter()
{
    cout << "Daughter Constructor!!" << endl;
}

Daughter::~Daughter()
{
    cout << "Daughter Deconstroctor" << endl;
}

main.cpp :-

#include<iostream>
#include "Mother.h"
#include "Daughter.h"
#include "GrandMother.h"
using namespace std;

int main(){
    //GrandMother granny;

    //Mother mom;

    Daughter baby;
}

When I am running the code, it's giving me the following error:- error: expected class-name before '{' token

Can anyone plz tell me what part of my code is wrong.

You have several errors in your header files. First, if `Mother` is going to inherit from `GrandMother`, then the definition of `GrandMother` must be visible before the definition of `Mother`--i.e. you need `#include "GrandMother.h"` in Mother.h and you need `#include "Mother.h"` in Daughter.h. You also need to make it so that Daughter.h actually defines a class named `Daughter`, with appropriately-named constructors and destructors and its own include guard, because right now it's identical to Mother.h (copy-paste error for the question?) — Nathan Pierson, Oct 04 '21 at 03:13
Furthermore I question the overall sense of this inheritance structure. You're saying every instance of a `Daughter` is also an instance of a `Mother` and a `GrandMother`? If this is a mandatory aspect of an assignment or something it can't be helped, obviously, but it's fairly strange. — Nathan Pierson, Oct 04 '21 at 03:15
Please [edit] your question to represent the actual code you are describing. — Drew Dormann, Oct 04 '21 at 03:26
Make your base class destructor `virtual` to prevent memory leakage and other disasters. It's a [common pitfall](https://stackoverflow.com/a/461224/4123703) for newcomer — Louis Go, Oct 04 '21 at 03:33

score 0 · Accepted Answer · answered Oct 04 '21 at 08:48

Your header are not self-contained, so you have to include them in right order:

#include "GrandMother.h"
#include "Mother.h"
#include "Daughter.h"

but it is fragile.

Right way is to make the header self contained:

#ifndef GRANDMOTHER_H
#define GRANDMOTHER_H

class GrandMother
{
public:
    GrandMother();
    ~GrandMother();
};

#endif // GRANDMOTHER_H

#ifndef MOTHER_H
#define MOTHER_H

#include "GrandMother.h"

class Mother: public GrandMother
{
public:
    Mother();
    ~Mother();
};

#endif // MOTHER_H

#ifndef DAUGHTER_H
#define DAUGHTER_H

#include "Mother.h"

class Daughter: public Mother
{
public:
    Daughter();
    ~Daughter();
};

#endif // DAUGHTER_H

Building simple function to inherit 3 classes in C++

1 Answers1