Question

I have a function in deck.cpp which deals random cards from a deck:

QVector<card> Deck::deal_rand_cards(QVector<card> vDeck, int quantity)
{

QVector<card> vDealt;
int deckSize = vDeck.size();
card randCard;

qsrand(QTime::currentTime().msec());


for (int i=0;i<quantity;i++)
{
    int rn=rand()%deckSize;
    randCard = vDeck[rn];
    qDebug()<<vDeck.size();

    vDealt.append(randCard);

    vDeck.remove(rn);
}

return vDealt;
}

My issue is that everytime the function is run from mainwindow.cpp, vDeck contains the full deck, instead of the deck minus dealt cards which i removed with the function.

If I deal 3 cards twice, debug prints:

54 53 52 54 53 52

How to update a variable within a function that is used by other functions and in other files? I have a feeling a pointer is involved, but I still don’t quite grasp the concept.

Thanks

here’s deck.h

#ifndef DECK_H
#define DECK_H
#include <QString>
#include <QVector>

struct card
{
    QString suit;
    QString color;
    int rank;
};

class Deck
{

private:
    int size;
    int jokers;

public:
    QVector<card> build_deck(int deckSize, int jokers);
    QVector<card> deal_rand_cards(QVector<card> vDeck, int quantity);

};

#endif // DECK_H

Answer 1

You need to pass reference of vDeck into deal_rand_cars function, currently you are working on a copy of vDeck.

QVector<card> deal_rand_cards(QVector<card> &vDeck, int quantity);
                                           ^^^ pass by reference

If you use a reference as an argument, the function works with the original data instead of with a copy.