Question

I have a problem. I’m trying to create an array of different class objects derived from a base class. This is the code:

 class Cdvd{
protected:
 char *numeArtist; //numer artist sau film
 char *tip;// CD sau DVD
 int cantitate; //numar de CD/DVD din baza de date
 int pret; //pret per unitate
 int cod_intern; //cod intern produs. Spre exemplu 0 pentru un film horror.
 void scriereInFisier(std::fstream &out); //scriere in fisierul cu produse
public:
 Cdvd(); //constructor produs implicit
 Cdvd(const Cdvd &cdvd); //constructor produs cu parametru alt produs
 Cdvd(char *artist, char *tip, int cant, int pret, int cod_int); //constructor produs cu parametri
 ~Cdvd(); //destructor produs
 char *getNume(); //returneaza pointer la numele artistului sau filmului
 void parseFis(char *artist, char *tip, int cant, int pret, int cod_int);
 virtual void afisCamp()=0; //afiseaza campurile produsului
};


class CD : public Cdvd{
private:
 char *genMuzica; //genul muzicii
 char *extensie; //extensia fisierelor audio
 int nrTrackuri; //numar melodii
 int lungime; //lungime totala melodii
public:
 CD(); //constructor implicit cd
 CD(char *artist, int cant, int pret, int cod_int, char *genMuzica, char *extensie, int nrTrackuri, int lungime);
 CD(const CD &cd); //constructor cd cu parametru alt cd
 ~CD(); //destructor cd

 void parseFis(char *artist, int cant, int pret, int cod_int, char *genMuzica, char *extensie, int nrTrackuri, int lungime);
 void afisCamp(); //afiseaza campurile cd-ului
};

class DVD : public Cdvd{
private:
 char *genFilm;
 char *extensie;
 int lungime;
public:
 DVD();
 DVD(char *artist, int cant, int pret, int cod_int, char *genFilm, char *extensie, int lungime);
 ~DVD(){cout<<"~DVD()"<<endl;};

 void parseFis(char *artist, int cant, int pret, int cod_int, char *genFilm, char *extensie, int lungime);
 void afisCamp();
};

Now, I’m trying to create from this class an array of CD and DVD:

class ListaProduse{
 static const int dimMax=20; //dimensiune maxima lista produse
 Cdvd **vector; //vector in care se retin produsele
 int nrProduse; //retine cate produse sunt in baza de date
public:
 ListaProduse();
 ~ListaProduse();
 void adauga(std::fstream &in);
 void afisare();
};

and this is the code for ListaProduse class:

ListaProduse::ListaProduse()
{
 nrProduse=0;
 vector=new Cdvd*[dimMax];
}

ListaProduse::~ListaProduse()
{
 if(nrProduse>0)
 {
  delete vector;
 }
}

void ListaProduse::adauga(std::fstream &in)
{
 if(in.is_open())
 {
  int pret,cant,cod;
  char temp1[20],aux1[20];
  char aux;

  while(!in.eof())
  {
   in>>aux;
   in>>temp1;
   char *teemp1=new char[strlen(temp1)+1];
   strcpy(teemp1,temp1);
   in>>pret;
   in>>cant;
   in>>cod;
   switch(aux){
    case 'C':{
     int nrTr,lung;
     in>>aux1;
     char *auxiliar1=new char[strlen(aux1)+1];
     strcpy(auxiliar1,aux1);
     in>>aux1;
     char *auxiliar2=new char[strlen(aux1)+1];
     strcpy(auxiliar2,aux1);
     in>>nrTr;
     in>>lung;
     CD *x;
     x=new CD;
     x->parseFis(teemp1,pret,cant,cod,auxiliar1,auxiliar2,nrTr,lung);
     vector[nrProduse]=x;
     vector[nrProduse]->afisCamp();
     //cout<<vector[nrProduse]->numeArtist;
     nrProduse++;
     break;
        }
    case 'D':{
     int lung;
     in>>aux1;
     char *auxiliar1=new char[strlen(aux1)+1];
     strcpy(auxiliar1,aux1);
     in>>aux1;
     char *auxiliar2=new char[strlen(aux1)+1];
     strcpy(auxiliar2,aux1);
     in>>lung;
     DVD *x;
     x=new DVD;
     x->parseFis(teemp1,pret,cant,cod,auxiliar1,auxiliar2,lung);
     vector[nrProduse]=x;
     vector[nrProduse]->afisCamp();
     nrProduse++;
     break;
        }
   };
  }
 }
}

void ListaProduse::afisare()
{
 if(nrProduse>0)
  for(int i=0;i<nrProduse;i++)
  {
   this->vector[nrProduse]->afisCamp();
  }
 else
  cout<<"Nu exista produse in baza de date!"<<endl;
}

Now I create in main an instance of ListaProduse. I call ListaProduse.adauga(filein) and then ListaProduse.afisare(). The problem is that when I call afisare() the program stop working and says:

Unhandled exception at 0x00ba3055 in
test.exe: 0xC0000005: Access violation
reading location 0xcdcdcdcd.

pointing to

this->vector[nrProduse]->afisCamp();

What could be the problem? Can anyone help me? Thanks!

Answer 1

Thank you very much. The problem was on

this->vector[nrProduse]->afiscamp();

It was supposed to be

this->vector[i]->afisCamp();

My mistake. 🙁 And the idea with std::vector is more than great, but I have to do my project (for school) using polymorphism.

Thank you again!