C++ Class inheritance in different files

Question

I'm trying to learn Inheritance mechanism in C++, I have made a Bancnote(Bills) class, and I want to make a class Card inheriting all the functions and variables from Class Bancnote.

And I get this type of error :

include\Card.h|6|error: expected class-name before '{' token|

BANCNOTE.H

   #ifndef BANCNOTE_H
#define BANCNOTE_H
#include <iostream>

#include "Card.h"
using namespace std;

class Bancnote
{
    public:
        Bancnote();
        Bancnote(string, int ,int ,int );
        ~Bancnote( );
        int getsumacash( );
        void setsumacash( int );
        int getsumaplata( );
        void setsumaplata( int );
        int getrest( );
        void setrest( int );
        string getnume( );
        void setnume( string );
        void ToString();


    protected:

    private:
        string nume;
        int sumacash;
        int rest;
        static int sumaplata;


};

#endif // BANCNOTE_H

BANCNOTE.CPP

#include <iostream>
#include "Bancnote.h"
#include "Card.h"
using namespace std;
int Bancnote::sumaplata=0;

Bancnote::Bancnote(string _nume,int _sumacash,int _rest, int _sumaplata )
{
    this->nume=_nume;
    this->sumacash=_sumacash;
    this->rest=_rest;
    this->sumaplata=_sumaplata;
}

Bancnote::Bancnote()
{
    this->nume="";
    this->sumacash=0;
    this->rest=0;
    this->sumaplata=0;
}

Bancnote::~Bancnote()
{
    cout<<"Obiectul"<<"->" <<this->nume<<"<-"<<"a fost sters cu succes";
}

string Bancnote::getnume()
{
    return nume;
}
void Bancnote::setnume(string _nume)
   {
      this->nume=_nume;
   }
int Bancnote::getsumacash()
{
    return sumacash;
}
void Bancnote::setsumacash(int _sumacash)
{
    this->sumacash=_sumacash;
}
int Bancnote::getsumaplata()
{
    return sumaplata;
}
void Bancnote::setsumaplata(int _sumaplata)
{
    this->sumaplata=_sumaplata;
}
int Bancnote::getrest()
{
    return rest;
}
void Bancnote::setrest(int _rest)
{
    this->rest=_rest;
}
void Bancnote::ToString()
{
    cout<< "-----"<<getnume()<< "-----"<<endl;
    cout<<"Suma Cash: "<<this->getsumacash()<<endl;
    cout<<"Suma spre plata: "<<this->getsumaplata()<<endl;
    cout<<"Restul:"<<this->getrest()<<endl;

}

CARD.H

#ifndef CARD_H
#define CARD_H
#include "Bancnote.h"

class Card: public Bancnote
{
public:
    Card();
    virtual ~Card();

protected:

private:
};

#endif // CARD_H

what is the question? I suppose it is "how to fix the error?", but then we need to see the code. Please read about [mcve] — 463035818_is_not_an_ai, Jan 11 '19 at 10:12
also please dont post the "type of error" but the exact error message you get — 463035818_is_not_an_ai, Jan 11 '19 at 10:12
I don't think a Card is a BankNote. Especially since BankNote has nothing virtual. Your design is wrong. Check the Liskov principle. — Matthieu Brucher, Jan 11 '19 at 10:16
Don't include `card.h` from `bancnote.h`. The effect of that is trying to derive `Card` from `Bancnote` before `Bancnote` is defined. Including `bancnote.h` from `card.h` (as you are) is fine, since that gets the order right. — Peter, Jan 11 '19 at 10:16
Get a good C++ book, there are so many bad things with your code :/ — Matthieu Brucher, Jan 11 '19 at 10:17
People sometimes "decorate" parameters in order to avoid writing `this->`. There is no point in doing both. — molbdnilo, Jan 11 '19 at 10:20
@molbdnilo in this instance, there is no need, as all arguments should be initialized properly with the initialization list, and the string probably moved. — Matthieu Brucher, Jan 11 '19 at 10:28
@MatthieuBrucher I was referring to the use of both an underscore prefix and `this->` in every function, not just the constructor. — molbdnilo, Jan 11 '19 at 11:11

463035818_is_not_an_ai · Answer 1 · 2019-01-11T10:25:47.827

You have messed up the includes. What you have is more or less this:

Bancnote.h:

#ifndef BANCNOTE_H
#define BANCNOTE_H
#include "Card.h"    // remove this

struct Bancnote {};
#endif

Card.h

#ifndef CARD_H
#define CARD_H
#include "Bancnote.h"

struct Card : Bancnote {};   // Bancnote is not yet declared
                             // when compiler reaches here

#endif

When in main you include Bancnote.h then this header includes Card.h so you try to declare Card before Bancnote is declared. Actually Bancnote does not need the definition of Card, so simply removing the include should fix it.

PS: there are other issues (see comments below your question). Most importantly it is not clear why a Card is a Bancnote. Second, never put a using namespace std; inside a header! (see here why)

C++ Class inheritance in different files

1 Answers1