How can I create a class that is a vector of another class in C++?

Question

Thanks for reading my question.

I'm trying to begin writing a program that uses a deck of cards, because I want to learn about using classes. I decided to create a class that stores a suit and a value, like so:

#ifndef CARD_H
#define CARD_H

class Card {        
    public:
        //here are the individual card values
        int _suit;
        int _value;
        Card(int suit, int value);
};

#endif

#include "card.h"

//define suits
const int spades = 0;
const int clubs = 1;
const int hearts = 2;
const int diamonds = 3;
//define face cards
const int jack = 11;
const int queen = 12;
const int king = 13;
const int ace = 14;

Card::Card(int suit, int value){
    _suit = suit;
    _value = value;
}

I then decided to create a deck class, and in that class initialize my cards by assigning a value from 0-3 (suit) and then a value from 2-14 (ranking of card). I also add the cards into a vector that I defined to hold them, like so:

#ifndef DECK_H
#define DECK_H

#include <vector>

class Deck {
    public:
        std::vector<Card> _deck(51);
        Deck();
};

#endif

#include <iostream>
#include <vector>

#include "card.h"
#include "deck.h"

const int all_suits = 4 - 1;
const int all_values = 14;

Deck::Deck(){
    int i = 0;
    for (int j = 0; j <= all_suits; ++j) {
        //begin with 2 because card can't have value 0
        for (int k = 2; k <= all_values; ++k) {
            _deck[i] = Card(j, k);
            ++i;
        }
    }
}   

This somehow gives me issues when I try to test the program like so:

#include <iostream>
#include <vector>

#include "card.h"
#include "deck.h"

int main() {
    Deck new_deck = Deck();
    std::cout << new_deck._deck[4]._value;
  return 0;
}

The following errors show up when I try to run the code:

In file included from main.cpp:6:
./deck.h:8:27: error: expected parameter declarator
                std::vector<Card> _deck(51);
                                        ^
./deck.h:8:27: error: expected ')'
./deck.h:8:26: note: to match this '('
                std::vector<Card> _deck(51);
                                       ^
main.cpp:22:24: error: reference to non-static member function must be called; did you mean to call it with no arguments?
        std::cout << new_deck._deck[4]._value;
                     ~~~~~~~~~^~~~~
                                   ()
3 errors generated.
In file included from deck.cpp:8:
./deck.h:8:27: error: expected parameter declarator
                std::vector<Card> _deck(51);
                                        ^
./deck.h:8:27: error: expected ')'
./deck.h:8:26: note: to match this '('
                std::vector<Card> _deck(51);
                                       ^
deck.cpp:18:4: error: reference to non-static member function must be called; did you mean to call it with no arguments?
                        _deck[i] = Card(j, k);
                        ^~~~~
                             ()
3 errors generated.

Honestly, I'm not quite sure what's going on. I pretty closely followed an example of classes I saw online. If anyone could help me find the problem, that would be much appreciated. Sorry, I'm a little new to this, and may have made some silly mistakes. I really appreciate your time and patience in reading this and helping me out.

Answer 1

Your problem lies with the declaration of _deck:

class Deck {
    public:
        std::vector<Card> _deck(51);

Here you are trying to declare _deck and call a constructor, but you can not do so from a class member initialiser. It's possible to do this for data members with no constructors, for example:

class Deck {
    public:
        int no_of_cards = 51;
        std::vector<Card> _deck;

You will need to use your constructor to initialise _deck (much like you're already doing:

Deck::Deck() {
    _deck.reserve(51);
    int i = 0;
    for (int j = 0; j <= all_suits; ++j) {
        //begin with 2 because card can't have value 0
        for (int k = 2; k <= all_values; ++k) {
            _deck.push_back(Card(j, k));
            ++i;
        }
    }
}

And leave your declaration of _deck as:

class Deck {
    public:
        std::vector<Card> _deck;